[jku72]

Slow down, your talking about a lot of money in all those things. The most important thing is to remember that the truck runs good now. Taking it apart only makes sense if you have a big amount of money and another car you wouldn't mind driving for a long time. A good paint job is going to be several thousand, an interior is going to be almost a thousand, and engine jobs take a long time, and even doing it yourself is going to be at least a thousand, for a stock rebuild, when you talley it all up.
Given my having been in your situation before, I suggest that you take small steps, save enough to do a COMPLETE job in any one area, then do just that one job, until that job is done, then you can reassess what the next step would be. In other words, dont remove the old interior until you have the new one ready to go in, dont tear apart the engine until you are ready and rich enough to do a complete job, and get it back running. I made those type mistakes on several cars, and ended up never finishing. It is a very difficult thing to avoid, the whole take it apart in advance out of eagerness, but if you do, you usually end up with a non-functional truck for a long time, and that stinks. Faded olive green paint looks way better than primer, so until you have the coin, resist the urge to sand it down in preparation for eventual paint job.
My 402 needs a rebuild, and it leaks oil out of the main seal, but I am not going to fix it right now, because I would rather pour oil through it than have a real nice lawn ornament for the summer.
I suggest keeping simple, if you want a nice sound, buy a set of headers and a complete dual exhaust kit, then thrash it in with friends on a weekend. Keep the upgrades small, like going to an HEI, and small stuff.
This is my opinion only, but boy oh boy, I hate to see projects where the goals were too ambitious and ended up not running or tore up.