Make sure that you lens will meter on the body you choose. Some of the later bodies, N series in particular, would not meter with older lenses because they didn't have electronic contacts. The N80/F80 is one example. The previous generation 8008 series would from what I remember. I'm not sure about the later N90 or F100 but I believe they did.
I wouldn't doubt that the FM3a would be a good fit.
If your 50/F1.2 is the AI version it was pretty good wide open, better stopped down slightly, but not so good beyond F8. Here's a good site for evaluations which speaks to it.