I have a 1974 350 block in my car (2 piece rear main seal). i am in the process of changing my 700R4 to a 5 speed.

i have an old 1 piece flywheel laying around, i know i cant use it, but why is the flexplate that came off my engine, and the 1 piece RMS flywheel such different sizes? (see pic)

do i have to get a different starter?
will the new 2 piece RMS flywheel be the same size as the flexplate i just took off my engine?

 

The 12-3/4", 153-tooth part is the one you should be using. You will need a different starter (nose, at least). One type has the mount bolts straight across from each other, the other has them staggered. IIRC, the large is staggered, the small is straight across (whichever it is, get the one that's different from what you have now).

It appears the flexplate came off the '74 engine. 3rd gens never used the 168-tooth, 14" flywheel or flexplate. If you buy a starter for a 3rd gen application, it will be the right one.

Oh, one- or two-piece rear main seal doesn't affect the starter. Flexplate/flywheel diameter does, and rear main seal affects the flexplate/flywheel bolt-up, but that's all the farther it goes.

 

thanks, thats exactly what i needed to know!!

my starter does have a staggered bolt pattern.