DIY machine work for heads??

Bronze guides on the street are fine. Done it more times than I can count. Bronze works great with stock valves or stainless.

The reason stock engines run iron guides is because it's cheaper to manufacture and they work, but bronze is better.

71produster, FYI - it's called "knurling". It's a process where a tool is run through the guide that basically threads the inside of the guide, making the diameter smaller, then a reamer is run through it making the clearance correct. It's old technology and it doesn't last. Usually, the guides are worn out again in a few thousand miles because, while you have tightened them up and allowed for more oil to get down into the guide, you have reduced the amount of surface area of the guide and they wear out quick.

Regarding the question about doing it yourself - don't even try. Your valves will be pointing every which way but where you want them. The tooling is very specialized and it needs to be done on a professional piece of equipment by somebody with experience. The first set I did when I was learning in school turned out pretty bad.