Great, you have it running now. Did you work out the vacuum lines, because it could take a while to get new or used items like that from the 90's?
That engine is a great platform for any upgrades. You could keep working on that one, but now you have the whole system working. If you can find another 351 engine I'd build the next one with more effort into the compression, heads, cam etc. You do need a better cam, just moving to a roller cam is a big step up.
I think your headers are great, and the PCM can support anything you do with the engine. I'd keep it NA and looking about like you have it, run a good 10:1, and TFS heads.
There is a lot to gain with TFS Twisted Wedge heads, those would be the best to match your stock port locations, bolt pattern etc. Anything better would not work with those headers, High Ports, Cleveland, Canfield for example.
The rest of all heads fall into the stock valve location/angle category, their potential is less than the Twisted Wedge heads, and the higher end. Given the same port sizeing or flow specs, the TW heads are faster. They cost the same as AFR, so get the TFS heads, 195 to 205 depending on your rpm range goals. I doubt that you would want bigger for the SUV, but you may.
I could build my SUV engine into a 7500rpm beast, but I would not like the high strung nature of that, in a truck.