1976 PCM 351

I have looked around this forum for some simple answers to my specific need, and cannot find the needle in the haystack. So, here it goes. I would like to eventually rebuild my 76 351. Wouldn't mind a few extra horses. Is porting the heads an option? Are GT40 heads the way to go? And, are there any rebuild "kits" available anywhere?

I understand that this is a major undertaking, with a reinstallation requiring lining up the block precisely and getting the flanges to the prop shaft to line up. I am mechanically inclined, but would need help understanding all of the "top dead center" stuff, what I should do, and what I shouldn't do. But at this point in time, I wouldn't mind chatting with someone that has gone through this before, and can give me a little insight/foresight.

Thanks again for taking the time to respond, I really appreciate it.
ps. the engine probably has a good 4000 hours on it. It really doesn't burn oil, or leak anywhere, and actually purrs at 3600 RPM.