So i bought a cheap engine with the idea of rebuilding it, i was hoping it was a 350 but when i got the casting number and the suffix/partial vin im thinking its a 307 casting=3970020 and the number on the front was 12w138183 v0914ckh. the ckh is what makes me think its not a 350 but the 12w138183 is confusing me some...any one know for sure, i looked online and im getting frustrated so i figured id ask?