first time trying this, so here goes - i recently took possession of a 1977 chevy C20 custom deluxe. love this truck belonged to my dad until his passing, needs some work done to it - i will be doing myself. i know for a fact he loved tinkering with it all the time, pulling the engine out and possibly rebuilding it or swapping out. before i start buying parts for it for a tune up, etc. i would like to make sure what size engine this is and not assume its a 350 in the blind. so i located the number stamped on the cylinder head pad on passenger side front. did not see a series of numbers and letters so i got a second person to verify what i saw - 5503 and seemed to be partially machined off !! could anyone out there please help me ? thanks.