Background:I have a 1990 heavy-duty - ZF - 5 speed transmission designed for a 1990, 460 big-block gas engined F-Series 4 x 4. A friend wants to mate this transmission up to an older, 1968 (??), big-block engine (390 through 460) he claims it is a 460 but I question that and I'm not really sure how to tell the difference from a quick glance. I'm not historically a Ford specialist. All I know for sure is that it is an older big block Ford engine.Questions:What are the comparability problems we will run into when attempting to mate these different vintages of components (i.e., 1968 & 1990)?The older style big block engine has a larger diameter hole in the end of the crankshaft for the transmission input shaft's pilot bearing to slide into to begin with, but we can machine out a new custom pilot bearing to compensate for the difference in the diameter of the newer transmissions input shaft end at the pilot bearing to resolve that problem. This should work shouldn't it?Does anyone know what flywheel comparability problems we might run into? Will the older engine's crank position the flywheel too far back into the belhousing? A crude benchtop measurement suggests that this is the case and that the end mounting surface of the older block's crank sets about .250 of an inch farther back into the bellhousing than is the case for a newer (say 1990) 460 crank. What vintage of flywheel should we use or does it matter. Also, will any specific engine size or year of flywheel resolve this issue of the older crank positioning the flywheel farther back into the bellhousing? Is this really a problem in the first place? What engine displacement and engine year flywheel should we be using for this match up?Does anyone out there know if there is a swap or parts comparability manual published somewhere that can definitively answer all these and other related swap and comparability questions?Does anyone have a Ford parts or Ford SVO contact telephone number and / or contact person I might use to attempt to get answers to these and related questions?I would appreciate any and all advice or leads to a source for answers to these and related questions.Thanks in advance for your help.CheersJohn Gilbert