my dillema

I have a 68 69 340 long block an a body 833 4 speed and all the stuff to do a 4 speed conversion but the retainer bearing hole in bell housing is too small and suspect the flywheel is wrong engine is not froze how can I tell if this stuff is good to go as the previous owner told we it was or find someone more knowladgble than me to eye ball it will 68 69 years have a different casting # I really made a lot of progress on this build in 2 months but now fuel brake electrical has slowed me down butView attachment 1715085426 would like to finish over the winter

questions:

Why do you suspect the flywheel is wrong?

What size bearing retainer is your 4 speed?