Originally Posted by 67-4-fun
i dont know much about the the newer style 350's builds, parts, clearences etc.. I need to learn more about them.. im more old school i guess. im taking more about the older blocks
The block being referred to is the '96-'00 RPO L31 Vortec 5700 350 motor found in Chevy and other GM brands. Look at trucks and vans of those years. Heavier vehicles had 4-bolt main caps, but they are not entirely necessary for a naturally-aspirated street build or street/bracket build. This is still a Gen I motor, same basic design as the '55-'86 block. The heads are the best production heads ever produced by Chevrolet, one-piece rear main seal and roller tappet cam. Generally, the stock roller tappets can be re-used with an aftermarket roller tappet cam.
Inlet ports on the L31 heads are taller than heads used on '55-'86 motors, requiring a dedicated Vortec intake manifold. NOW HEAR THIS....'55-'86 cylinder heads will fit on this block, but if you use the L31 heads and plan to use a carb instead of EFI, you will need an aftermarket Vortec intake manifold such as an Edelbrock #7116 Performer RPM intake.