The 502 engine is a marine or a crate engine
never installed in any car or truck from the factory.
4 bolt mains
Gen IV and GEN VI head will interchange-----GEN V needs a special head gasket.
Gen V engines have a stamped steel front timing cover with 10 bolts
Gen VI engines have a cast aluminum cover with 6 bolts
Gen V are flat tappet cam engines
Gen VI are roller cammed engines