Well, it's been too many years ago to remember! But, I do recall it was trial and error. It is helpful to be sure to remove both original factory side steady rests from the engine so it can rock side to side, also the oil filter. I have an AOD so no clutch linkage. Also, I no longer use my power brake unit so that has been removed, so you may need to temporarily move it.
Again I recommend the short set screw type studs to make it easier to position the gaskets on the install. The shortening of the rod and attachment collar will help some to lean over the rod towards the engine. I also didn't use the rubber steady rest bushings when fitting things up this will give you more room to experiment with your application.
Also, I just remembered that the battery and tray is in the way, so you may want to remove them as well. My battery is trunk mounted so I have much more room.
Hope that helps a bit. The headers WILL go in but your results may vary. I can shoot more pics if you need or try to answer more specifics if you want just let me know. Let us know how it's going.
A L A N F R A K E S ~ Tulsa, OK