If your truck is carbureted, then you're in luck. If it's original, it should be. I have an 87 & got stuck with TBI, which means I have to stick with TBI replacements unless I do alot of re-routing & changing things. If you go with a big block, you'll have to replace & change motor mounts, & other things.
I say your best bet is to search the newspapers & traderonline.com for a 350 motor, which should be like finding a Wal mart-easy. next call northern auto at 800-831-0884 & you can get a 383 rebuild kit with all necessary parts for $650. Jegs & Summit are too expensive. Installation should run about 400-700 if you shop around & find a reputable mechanic. All told you should have maybe 1500-1700 in the whole kit & kaboodle, & it'll eat a 2000 Silverado alive.......... Heck, it'll eat alot of cars alive, depending on your axle ratio. It'll whoop a big block too, unless it's beefed as well. Best bet & bang for the $$$ is a 383 stroker!
Making money off of Mother Nature