overheating/headgaskets/

I have recently put back together after two years , a 1993 lumie. The head gaskets were blown. Some one else had replaced the heads and gaskets, I put the rest of it together and was running great. The temp sensor was reading up and down. Now the gaskets seem to be leaking, white smoke out the tail pipe. I did a compresson test and the #6 and #1 are reading low 100. Is it possible that the gaskets were but on backwards? Or are the heads warped , or will I be doing this again and again tell I get the temp problem fixed ? Please help.

fyi aluminum heads should be shaved if aver taken off great possibility of warpage.