My friend recently bought a gm crate motor used but it did not come with flywheel. It is the basic 4 bolt main 350 with stock internals. My friend wants to replace the flywheel with a centerforce one but we dont know which one to get: the one with 153t up to 85 or the 153t 86 and up. Any advice is much appreciated.

 

i do believe it is the rear seal that matters 2 piece or 1 piece most likely its a 2 piece rear main.

what was the engine that was in the car org??

 

the 153 tooth or 168 tooth depends on what size clutch u are running

and based on that flywheel is what starter u need to get, straightline bolt or offset bolts

153 tooth flywheel uses 10.5" clutches and an inline bolt pattern on the starter
168tooth accomodates 10.5" or 11" and uses offsdet bolt pattern starter

there are one piece and two piece rear main seal designs
the one piece design started in 1986 and up
the crank flange for the flywheel has a smaller bolt pattern, so the flywheels have a smaller bolt pattern

look at the crank flange
if it is perfectly round and has a bracket bolted to the back of the block holding the one piece rear main seal
then get the 153tooth flywheel with the smaller bolt pattern

if it is a two piece rear main seal with an eccentric crank flange then its your choice of 153 or 168 as long as it has the larger bolt pattern