Either got ot the Holley site and do a search for that list number, or go to your local speed shop and check their reference material. Find the original sizes for everything and start there. You wil probably find it to be slightly rich with that size. But at least you'll start in the ball park and not hurt the engine.

      Look at the FRONT of the carburettor. The choke tower is the area at the top that the choke plate is mounted in. The front of the tower is the higher side, on the diver's side front you should find numbers stamped, they may be a Ford number or a Holley number, but either way that's your list number.

      The 731's are close tolerance 73's and that does sound big. HOWEVER, the factory jetting is established on a flow bench and by testing, they know what they're doing. I would NOT deviate more than 3 or 4 sizes either way without wondering what else is wrong. As far as the secondary plate goes, they're easy to change, but don't mess with it until you see what you have ON THE ENGINE. Don't guess. 

Like Frank mentions, baseline jetting should be the stock jets for that particular carb.  Using the jet sizes for the stock 1957 List #1273 Holley carb as a baseline for anything other than this simply doesn’t work.  As an example, there are a multitude of different list number 600 cfm Holleys out there and most have different baseline jetting requirements.  The air bleed sizes dictate this to a large degree and because of this, baseline jetting for each will vary.

And as Gary brings up, a smaller sized carb will have a higher velocity which in turn promotes improved atomization of the fuel (smaller droplets) which in turn will burn more of the fuel.  A carburetor that’s larger will have a slower velocity which will have weaker signal in which to draw fuel through its circuitry and also atomize the fuel at the venturi.  As a rule of thumb, increased velocity equates to increased torque.

Jet sizing is more related to the venturi size and the associated air bleeds within the carburetor and not the size of the engine for which the carb is being installed on.  The vacuum signal as well as the exhaust flow of the engine on which the carb is being installed on my dictate a given amount of jet change from baseline but there is no rule of thumb saying bigger or smaller jets when switching the same carb on a different sized engine.  If a carb is specifically designed for a small cubic inch engine and is then re-installed on a much larger one, then the potential for it running rich at idle is high due to the fuel transition slot being more exposed.  The first thought is to put in smaller jets but this simply puts the engine in a lean condition at the higher rpms.  Likewise, taking a carb designed for a large cubic inche engine and reinstalling on a small one will have the transition slots not exposed enough and creates a situation where a dead spot off of idle exists.  In both of these cases, more most be done to the carbs than a simple jet change to address the different issues.

      NO!  The carb doesn't care what size the engine is. It only reads airflow. As Ted mentions there's a lot of factors that affect the mixture, but the jetting is based strictly on airflow through the venturii, period.

                                           Frank

Pete didn't mention which of the vacuum secondary springs he's got in there but....get a stiff one - the 292 won't need the extra capacity at quite the same engine speed as your old 460. I usually just put the Holley heavy black spring in there and worry about opening the thing quicker somewhere off in the future.

The four barrel will look better on your toy anyway!.......