Replacement engine for 2002 Silverado with 5.3?

I inherited my fathers old 2002 Silverado with a 5.3 vortec with 320k miles on the clock. I'm in the process of fixing up the truck and making it more reliable as an around the town vehicle. The transmission was rebuilt 10k miles ago and feels solid but I want to have a plan in place if/when the engine finally goes out. Is the general consensus to find a junkyard replacement of the same engine with 100k or so miles and do a direct drop in? I'm looking to keep the truck as long as I can while not spending crazy money on some crate engine.