Frequently you can find 6.2 engines on Ebay for less than 1000 dollars. Most will be Humvee exchanges.
If your engine failed because of continuous high rpm operation and that is the way you use your truck, I would do the 350 swap. They can stand the rpm a lot better than a 6.2 can, anything over about 55 is screaming for a 6.2, 50 is better.
You can take your block and have it magnifluxed for cracks in the main bearing webbing. Normally when the bearings fail, it is actually the block that failed, allowing the bearing to spin. If it just needs a crank clean up and a set of bearings, that would be cheapest. Did the engine run good before it started hammering? Glen