318 head casting issues?

I bought a 318 for a project I am working on. The engine appeared to be all original, but now I'm not quite sure. The casting numbers on the engine say its a 1971. Is was told it was out of a camper. The transmission was attached and its definitely a camper transmission. My dad pulled the heads on the engine today and from what I can tell the casting numbers are from a 1960's 273ci truck engine. We measured the valves and they measure 1.88 and not 1.78 though.

Here is the casting numbers, and all other numbers I can find off of the heads. Any information you guys can provide would be greatly appreciated.

2658234-1 TRUCK
AAWJ
123
234-1
651

Thanks guys!