I have a question hopefully someone can help me with... Can a set of 400 heads be used on a 350? I know 350 heads can go on a 400, but must have the steam holes drilled. If I used 400 heads on a 350, do I need to do anything with the steam holes, or will the simply seal because the 350 block doesn't have them? Should I use a 350 or 400 head gasket, and would I have any extra power from doing this. I heard by putting 400 heads on a 350, it would increase mid and upper range hp.