The Mustang alternator uses the original Y-Block brackets with the addition of one long spacer on top, and a "Z" bracket to the adjustment bracket on the bottom.  As with the original setup, the new alternator belt is fully adjustable.

I don't want to rain on your thread, but check out my retrofit.  It was done years ago.

The factory slotted adjustment is still intact, however as you can see in this picture, the alternator is about against the engine block, and the slot is about out of adjustment.  Not too good for installing and tightening belts.

Looking at the front of the block, it would have been a major undertaking to remove the slotted bracket to prep it for modification, unlike the top front bracket which was held on by only two bolts. 

So my solution was to leave the factory bracket intact, and use this bracket I fabricated:

......to extend the range of the factory slotted bracket and still get the mod done in a day.  It gives me an inch or so of adjustment, and if that is not enough, the center bolt can be removed for even more adjustment.  I did some calculating of belt sizing and alternator positioning on AutoCAD today, so I've got it narrowed down pretty good based on the size that didn't fit yesterday.  So I'll see what they have close to the sizes I came up with.   

I appreciate the input on the Mustang alternator, I was just trying to find something with an internal regulator to eliminate some of the clutter on the firewall.  You don't see much documented on these conversions, so I thought I'd do so in case someone else had similar plans.  This will be my first use of a GM 1 wire, but with a 5 speed Clark trans, a 3 speed White Auxiliary, and tandem 8.50:1 Rockwells, there will be ample opportunity to rev the engine a bit to excite the alternator:

The last conversion to alternator I did was on a 56 panel, 272, and I again used an internal regulated alternator.  I think it was using an early 80's toyota or such P/U, the only mod done to the brackets were to cut off the rear tab on the generator mount and move it forward and weld to hold the back side of the alt.  Belts lined up perfect, I just couldn't remember exactly which alternator it was to use it again....  

Nice job on your retrofit.  You are going in the right direction converting to 12-v.
Six volt components cost twice as much as 12-v (especially car batteries).  Try to find a 6-volt GPS, power inverter to 115vac, cell phone charger, burglar alarm/remote start, stereo CD player, A/C compressor, W/S wipers, etc.

Oh, I forgot to mention: The '90 Mustang alt is internally regulated.  The wires go to Batt POS & NEG, and the key switch.  Pretty much single wire with the addition of the key sw wire.  It also charges immediately upon startup.  Remote Start Systems keep cranking the starter until it sees 14 volts (an indicator your engine is running because the alt is producing power).

Thanks!

You get a choice.  The one I like for Y-Blocks is this alternator:
 
It outputs 75-amps, and brushes are under $4.  Here are the applications:

If you like the more modern 130-amp Mustang alternator, here it is:

Notice the fan is on the inside.  Here are the applications:

Notice the top three BIG BK/O (black with orange) wires that all go to BATTERY?  Ford couldn't run 75-amps through two wires, so they use three.

White w/ Black goes from one plug to the other (for feedback to the regulator).

The third wire LG/R, senses the IGNition switch is on.

Ground is through the aluminum case.

If you want to copy the picture, RIGHT click on it and choose "Save Target As...".  Then save it to your folder of choice.

Dave Dare

I got the new alternator belt in, and it placed the alternator just where I wanted it, although the bracket I made is at the end of it's limits (in the end of the slot)  This calls for a another new bracket, just got it painted this evening, will get it installed this weekend. 

Robert

Robert, my purpose is to let people know that a GM 1-wire alternator works differently.  It has a unique quirk that most Ford users aren't used to.  As long as that is understood, then, ok!  It's NOT simply a one-wire and you're done (although it looks like it).  In order to eliminate the small "sense" wire that Ford uses, GM made a sacrifice that may play hell with a remote start or other accessories.

Yes, I come from Ford, but I also believe the best part for the application should be considered.  In your case, the Mustang alternator works like you would expect, pumping 14-volts as soon as it starts turning,  but it uses two wires (battery and sense) instead of one.

As long as you know to goose the gas past 1,500 rpm to get your GM alternator going, and you are comfy with that, ok!  Don't forget later on, upon initial start your battery is draining while idling; it doesn't mean the alternator is broken.  That is how the 1-wire must work.

Most non-electrical guys would jump on the GM alternator because it looks so easy.  I don't want anyone to buy one and find out it really isn't what they expected it should be, that's all.  Most places won't take back electrical devices, so it's "buyer beware."

 -  Dave

Dave, thanks for the clarification.  Although this truck will have only the basic stuff for electronics, it's nice to be able to compare the features pro/con to make an informed decision.  I didn't find much available in researching the 12v conversions three weeks ago when I started this venture, that's why I thought to start a thread to document it.  Perhaps you could post your conversion in more detail here as well to have a better resource for future use. 

I want to say, "just throw them away" but some Ford regulators use these posts as a tie-point, to pick up power for other things (like the horn relay).  Since the regulator will no longer be used, take it & the capacitor (and ground wire) off.

The regulator wires (GND, Field & Armature) going to the old generator: Remove them. They aren't big enough to carry 75-amps.

The regulator's BATTery wire can be spliced to the horn relay.

I do not wish to hijack this thread or bash the 1-wire alternator, but I am a licensed Electrician and a Ford employee of over 35 years.

The correct way to wire, includes a three-wire alternator, and a central tie-point where constant +12-volt wires should connect, including the key switch.  Remember, the key switch feeds your ignition circuit.  A small voltage drop drastically degrades ignition efficiency.  If that happens, the "sense" wire calls for more alternator voltage until it comes up to 14 (at the sense wire).  A 1-wire alt has no "sense" wire.

The stranded copper #6-AWG alternator wire can go to the battery side of the starter relay, or to the battery.  This wire is usually not fused.  Two things play a vital roll:  The wire is in free air, and it is short.  Otherwise, #6 could never safely carry more than 60-amps without overheating.

I also run a #1-AWG welding wire from the bell housing/starter area to the battery neg.  If you need a good ground for your distributor, this area is a good source and it's already connected to the rubber mounted engine.  A good ground like this, will wake up your starter motor.
Dave Dare

Dave, thanks for posting the connection info on the Mustang alternator, it will come in handy tomorrow as we wire up a 65 Fairlane to get it ready for the strip (in the assembly stage now).