Jeep 4.0 in 69 Barracuda
I knew 2 of the 3 you mentioned...just everybody else's parts, and just empty every pocket--although, I've experienced the last one too...just expect endless problems. A friend's '82 CJ7 absolutely ATE a left front hub on one weekend. Turns out he didn't fully wash out some debris after a rather extended trip in the mud...then we drove it about 400 miles to visit some friends of mine...there went about $500 for new hub, new rotor, new caliper, pads, etc.
The other time, he had to buy conversion axles for his AMC 20 rear end--the factory style are a two piece design and the conversion axles are one piece, but they aren't cheap...I think he sold it before actually getting around to changing them...at a loss of course.
Then, one of my roommates used to have an '89 YJ...4" lift, wheels/tires...needed the double jointed rear driveshaft, but never got around to it. Then we swapped an AMC 304 in it, installed an EFI conversion...I don't think the stock A999 trans liked that though...it ALWAYS ran hot and damn near boiled over one weekend just towing a frikkin sea doo to the local lake...constant problems. Hindsight being 20/20, we should've just rodded the carbed 4.2 that was installed ('89 was the last year for the 4.2, IIRC)
By comparison, the Cherokee guys I knew had far fewer issues but they didn't ride theirs' anywhere near as hard.
I can't wait to see how this works out because I think that 6 ought to be a great engine for a Barracuda--especially if you put some goodies into it. If it can move a 4200lb Wrangler around with that level of authority, a 3200lb A body should be fun to drive.