Here are a few words from someone who really shouldn't be giving advice, but I'll tell you what I have done on my own truck. When I first got started working on it, I had to deal with both bent pushrods and stuck valves. The guides and seals were none too healthy, and in any event those old valves always wore fast. The head needed to be rebuilt, so I lifted the head off and left it to a machine shop. It cost a few hundred bucks plus the parts, but they did all the work and it was well done. I replaced all the valves and seats with modern harder valves in the hope that I can burn unleaded without worrying about what I might damage, on the recommendation of the garage that did the work.
One thing I did not do which I am sorry about is repaint the head before putting it back in. But with the newly rebuilt head the motor runs like a charm. I did not do anything to the rest of the block, but that will have to happen in a few years too. The truck runs great. I had to set the valves roughly to get it running and to warm the engine up, then reset them with the engine warm, but you can read about that from any number of books or earlier posts from people who know a whole lot more than I do.
As far as what head to use, you are going to have to mess with either of the heads, so its just to choose one. I would take the older head, but that is just because I would rather keep the engine as original as possible. But unless you've done this kind of work before, leave it to a machine shop I say.
