how about a sereial number, not a casting number if you want real meaningfull info on your tractor.
pic will help too.
tip: all gassers pre 65 were 6v positive ground.
all diesel were 12v negative ground.
Guessing you meant conn 6015G
C0NN-6015G - 134 sleeveless late 1962-1964
Sounds like you will be looking at a 601 or 2000.. assuming oe engine
post more details.
here is a bit of info on iding a tractor. the first part is about N's.. last part about units with your engine code.