Parts ID info????

Hello,
I got a set of heads with my truck,I saw a crack between the valves...now I can't find it.I don't know if they are 6.2 or 6.5 can you tell me the casting numbers for 6.5 turbo heads??? Also I got an extra turbo,I guess it's what you guys are calling an "8" the one on the truck is a "3" is the 8 better?? I'm going to go to a man. boost set up ASAP,(when I get the money)But I thought about the extra heads checked out and put them on it just to be sure.I know I at least have a bad gasket now...I'll get the casting numbers and post them ASAP.

Thanks Tom K.