If you can find a first generation 350 Vortec full size (C/K-1500) pickup, she'll have plenty of power. The plain Jane version produced 255 HP, but the best part is how they perk up with just the mildest of improvements. You see, the first gen Vortec truck heads flow better than the aftermarket aluminum stuff. A mild port job, relieving the intake side of the guide bosses, polishing the exhaust side, after relieving their bosses and you've got an extra 25 HP. Toss on a few other basic parts, like an intake (replacing the two piece factory unit, which tended to leak) and you can get 300 HP with the same ECM, injectors and everything else. Some "re-mapping" will be necessary, but this is real easy too, if you have a cable and a laptop. The best versions of these are the OBDII's from '96 to '99 (maybe up to '02, but I'm not sure).
You can pick up a C or K-1500 for not a lot of money. I see them in good shape for $1,500, of course with high mileage. If you don't want to bother with the rebuild, porting and all that, a long block, direct from GM is about 2K or you can get an aftermarket long block for about $1,500. You just transfer all your stuff, (intake, fuel rails, alternator, etc.) and she's good to go. Unfortunately, the transmission isn't the same deal, unless it's a manual. The 4L60 (or 80) E automatic is a costly swap out, so it's usually best to just have what you got, rebuilt or find a manual, which typically only need a clutch, synchronizers, throwout bearing and a new pilot bearing.
You can make one of these trucks just like new, if you toss a few grand at the various elements. I just did all the front end parts, upper and lower ball joints, A arm bushings, tie rods, pitman and idler, and bushings. Hard, dirty work, but just one afternoon and it's all new and tight again. About $300 in parts and a half a tub of GoJo, plus some cussing on the lower A arm bushings (hard to make a tool to remove the old ones).
Simply put, you can join the book of the month club, or with 2K on the engine, another 2K on the chassis and rubber (door seals, window glass seals, body bushings, etc.), maybe another 1K on other assorted stuff, you have a reliable, feels and drives like new, ride and with some research, one that gets better fuel mileage too. I've jacked the combined mileage from 17 to 21, just with minor mods (headers, TB spacers, roller rockers, etc.). With a full up re-map, I could get in the 24 MPG range, but I'd lose a bit of power.