newbie from idaho needs help!

first I,d like to say hello and that i am so glad that i came across this web site. I am in the middle of restoring a 70 belvedere with a 318. the engine had a badly cracked block so i picked up a 318 out of a 69 pickup. when i got the engine home and cleaned it up I found that the motor was a 1974,which I think I am ok with. the problem I am having is identifying the heads that are on it. the casting # is 3870277 it also has the word truck cast into one of the intake runners. I have been to many web sites that have casting #s but have not found this one. It would be great if someone out there could help me with this. thanks and its great to be here.:banghead: