Unless you do all the work yourself aside from the machining, rebuilding the 3.0 could cost as much as swapping in a junkyard 3.4 v6. If you dont have a knock and haven't run it for a while with milkshake in the lower end you probably could just use head gaskets/head rebuilds. If it's a clean truck and you like it fix it, if not there are plenty of people who would take it off your hands and probably let you keep the 3.0 for free. Then you could use it to replace one of your 258's or whatever is in those Heeps. Congrats on the FJ, thats probably why you don't care to fix this truck.
I gotta slip in one heep comment lol, in the shop I worked at (I've only worked in one full service repair shop) I'd say 90% of my job was doing crank sensors and panhard bars on Cherokees, and oil cooler lines on S10 Blazers. Ok I'm done now. Oh yeah, and I think I fixed 1-2 ford ranger rear ends a month.