1979 2 door caprice

alright so heres the deal, i have a 1979 2 door caprice in which the body frame etc is in perfect condition, but the engine is a tired old 305 backed by a th-350. my plans are to pull the motor out and replace it(minus all the useless shit like emissions stuff) with a mildly built 350 that will produce somewhere around 350hp. am i right in assuming the th-350 will be able to hold up for a good while, it currently has 90k on it. also i plan on adding headers. i already have a true dual set up on it, but i plan on redoing it so i can remove the cats and change the mufflers to cherrybomb glass packs. anyone care to share thoughts, advice, hints, tips etc? im trying to keep myself on a budget, so ive been looking for a motor on craigslist. anything special i should be looking for? im not interested in keeping it original at all, i just wanna make it a nice cruiser on a budget. i appreciate anything and everything you guys will have to say.