Slant 6 swap 170 to 225

The slant six crank flange was enlarged 1/4 inch beginning with the 1968 model year. So your 65 flywheel won't bolt up to a 74 crank as is. However, you don't have to change flywheels. Just take your 65 flywheel to a machine shop and have the center hole enlarged to fit the post-67 225 crank. Will work fine. The pilot bushing is a different issue; most automatic transmission cranks - V8 or six - are not fully machined for a pilot bushing. You might luck out and have an automatic-transmission 225 that has a fully machined pilot hole. If not, NAPA used to offer a conversion bushing that would fit in the semi-finished pilot hole in the crank, but I think they are NLA. Not a problem these days, as the readily-available pilot roller bearing that came on manual trans Dakotas and probably others will fit just fine and will work better than the conversion bushing anyway.