Hi and welcome to mightyram. This is a tricky question. First up - this is the original engine right? And secondly, do you want to keep your truck 'matching numbers'? You are right about finding a good used engine from a JY. The G54B has inherent issues with cracking heads (mostly with engines using jet valves) so my bet would be a lot of these trucks end up getting scrapped due to this problem. It's done pretty good for 320,000 miles. You have options - used running engine from another truck, production line recon'd engine, rebuild your own engine or a drivetrain swap from a 2.0 ram50/mighty max (easier engine to work on and seems to be less prone to head failures but this doesn't mean they don't have other quirks...), or a big upgrade like a StarQuest 2.6 turbo which needs all the ancillary gear to make it work. Building an engine properly isn't cheap. Most of your cash goes into machine shop costs (crank, flywheel, block and head refacing) but if you're up to buying parts and assembling it yourself you'll save a stack of cash. I would consider getting a lower mileage engine and run that while rebuilding your original engine. You can make a number of modifications while rebuilding it to improve performance and you won't be stranded without a running truck.