No way in hell that thing needs a whole new engine. New lifters and pushrods and she'll be good to go. Cam damage is unlikely but possible. If it were mine, I'd tear it down and have a look. You can use factory parts, switch off AFM with a CARB-certified tune, and run it another 250K, easy. If you're on a tight budget and get the parts from RockAuto, I'll bet you can get it humming like new again for $500 in parts and a weekend. You can borrow all of the specialty tools you'll need like the harmonic balancer puller and PS pump pulley puller for free from your local Autozone.