As I reassemble my 360 that I bought used (took it apart to see what was in it and check its condition), I'm looking over the heads now. Ferrea stainless valves (2.02 intakes), ported, Crane Gold Rockers, aftermarket retainers, springs and keepers. As was the rest of the engine, they're in nice shape- almost. The builder (unknown) didn't install bronze guides. Some of the exhaust valve guides are a little loose. I can only imagine they're wearing quickly, because the rest of the engine showed little wear. It has a MP 292-508 cam. I haven't checked rocker geometry yet.
Is there a reason why someone would not install bronze guides?