On some early transmissions the neck of the converter extended to fit inside of the end of the crankshaft where the pilot bearing would reside. It should not be an issue on a 350TH.
A V-8 would normally use a 168 tooth flex plate. Small blocks are internally balanced. The flex plate would be balanced separately.
Since a 56 did not come with a 283 you probably have a later model engine. Something you should check is for the starter mounting boss on the engine. Your original starter mounted on the stick shift bellhousing. With the auto it needs to mount to the block. If it is an early block and is not drilled, an adaptor plate can be puchased from various aftermarket suppliers.
I have seen many of these conversions and don't know of anyone modifying the firewall or the floor pan.
Fred
Last edited by rfs56trk; 01/06/2009 4:44 AM.
