The c5 is not as good a choice as the C4- it was used behind 4 and 6 cyls, so not quite as strong. The C4 will be your easiest and they're cheap to find/build. Maybe sell the 5 and use the $ for a 4. Or, if you're looking for highway gearing or mpg, why not go with an AOD and get the overdrive? I did in a 65 and love it! As far as the flywheel, the weaight is pertaining to the engine, not the trans- so use the one you have on the engine as long as the tooth count is correct. good luck
Bad info on the C5. It is an upgrade over the C4. Main benefit of the C5 is better oiling passages.
There are 2 types of people, those who own pickups and those who borrow them.
69 M code Mach 1, 393w AFR 185, AOD trans, 3.50 traction lok N case, 14" 2015 Brembo 4 piston disc, QA1 4 wheel coil covers, Chromo tube susp arms, Triangulated rear arms, Convertible inner rockers & seat riser, 8 point roll bar.
Build Pics http://s782.photobucket.com/user/rob...?sort=3&page=2