Engine questions

I recently got a 1992 Mazda B-2200 with the F2G8 fuel injected motor,

So far it has a c-notched frame, the top end removed, the interior gutted, the tortions cranked so its riding on the bump stops and 3 inch blocks in the rear, but I have a few technical questions that have been bugging me and I haven't been able to get any answers.

Will pacesetter headers mess around with my fuel injection at all?
Like I know I have to weld an o2 bung onto the headers but is that all I'll need to do?

Also what kind of options do I have for a different fuel rail - camshaft and a ram intake?

Will I be able to switch over a head from a mazda 626, mx6 or anything else with more than 8 valves from the f2 block without any problems?