390 is the FE engine, and it had been installed in earlier trucks that also had the 289 / 302 as an optional engine.
However, tranny and motor mounts will be different. Your truck never had a 390 as an option, so will be a little harder.
I have rebuilt 3 FE engines, and the parts are a little harder to find these days. A good aluminum intake manifold and set of headers
are hard to find at a reasonable cost. I agree on the price, I usually get one for free and put $600 or more into it during the rebuild.
I do this when I am replacing an engine in an original car or truck that had one as an option to begin with.
My recommendation is - forget it! For more power, find a good 429 or 460 from an old Lincoln, and get a mail order installation kit.
even at that, the tranny will be different.