i just bought a 283 from a guy near my house. i paid $125 for the block and it had just been rebuilt so i got a pretty good deal. first thing i did when i got it was go to mortec and run the casting number it showed 283 2 bolt main well upon further examination i saw that my block was a 4 bolt main this puzzled me because chevy never made a 4 bolt main 283 i guess someone made it 4 bolt main but that just seems like alot of trouble to go through whats going on anybody have any idea i know what a 4 bolt main looks like im no fool and this is a 4 bolt main