I'm milling .025 off my heads to raise the compression a little. Would you use the std. .060" thick intake manifold gaskets or .120"?

The standart gasket should still work. You normally dont get in alignment issues until you go over 40 on heads. Food for though, when milling a head, you generally only get but 1cc per 5 thousands. You can put cometic gaskets on that are only .027 thick. That is like decking the block 13 thousands. With the gaskets, you get the full bore, decking the heads on gives you the chamber. You will end up the same and save all the expense to mill the heads. Those heads are thin anyway

Do you have the non ajustable valve train still? If so, you will need to make sure that you dont bottom out the lifters either way you go.

I did .020 on set and had no issues using standard intake gaskets. The machine shop said I could .030 without a problem. Also keep in mind that head gasket thickness can play a roll as well. They can vary from about .020-.060 thickness depending on what you use. Stcok merc is .030 and most of the standard Fel Pro's are .039.

Every 502 I have taken apart had the GM head gasket which is .041.

I had my AFR heads surfaced just enough to clean them up (I think about .008-.010)and my intake alignment was terrible with std intake gskts. I used the thicker ones and it was nearly perfect,a trick I found is you can look down the injector holes and see alot of the port to get a good idea of how its lining up,Smitty