That's a hell of a clean truck. I say keep it stock; finding another original 1st gen in that condition would be about impossible.
I would definitely say flip it for some profit and find another if you're wanting to mod.
I see you're in the metroplex. There is a first generation out here (Midland/Odessa) on a used lot. Looks decent from just driving by, but not this clean (I can see some fender rust). If you end up in the market for one to mod, I'd be glad to check it out (for you, or anybody else).