decode my v6

[oldno7]

http://67-72chevytrucks.com/vboard/a...01&d=136676788

So im thinking about these motors I found and thought they would be good for my c-30 project. There is 2 v-6 gmc motors that this older fella has One is to be a 401 magnum and the other is a 305. Here are a few pics I took of one of the motors and these are some numbers i got i think these were on the exhaust manifold and was wondering if you guys could help me figure this out or will i just need to go back and get info of front of motor.