Thanks Guys. Yeah, I brought it from OK to AZ via side trip up to south Colorado, so it got a good chance to stretch it's legs, though the old engine felt a little tired on climbs. Had to sort a few issues on the way but nothing that couldn't be handled on the road.
It wasn't till I tried to take it up north that it decided to spring a coolant leak in the night during the first heavier rain I ever drove it through, in the middle of the Mohave desert, and pulled a sleeve before it even registered too hot, as the original early '60s "dry block" 8v71s tended to do, before it even registered hot.
With the help of a vintage bus mechanics FB group I found an old timer detroit guy pretty close that turned out to be one of the gurus. He was busy with his wife who was recovering from a stroke, but told me he'd help me out if I did all the grunt work, for a very reasonable fee, and let me store it at his place.
It wasn't worth throwing money at rebuilding a dry block, but I was lucky enough to find a deal close to home on a newer design, 70's "wet block" pulled from an AM General city bus conversion (probably ex-Seattle Metro) that a tree fell on. It was recently rebuilt with few hours by the looks of it, on the cradle with transmission, accessories, and all. Trailered it down there at the beginning of the summer and spent most of the last year off and on working on it. Here's some video from the maiden voyage with the new engine. Dual 4" straight pipes, feels like you're flying a B-17 through town.