Whelp, I guess this thread is drawing to a close.
The Fossil sat in the yard for a few weeks because I had an intermittent no start issue, and I also had no power steering at low RPM. I replaced the shutoff solenoid on the pump but it did not help the starting problem, but I have been picking away at small jobs including chasing down some air leaks, and as a result starting it quite regularly. The starting frequency improved gradually over time, and after a while it would start every time, although sometimes it takes a little cranking. There is an internal check valve in the pump, and I have decided it is sticky and sometimes not holding pressure. But with new filters and fuel perhaps it is sorting itself out but I see a new pump in my future. I replaced most of the ancillary systems when I refreshed the motor but I just resealed the pump and threw it back on since it ran well enough in the Freightliner.
The steering issue turned out to also be a worn out pump. I did not zoom in on that right away because the Freightliner turned well and so did the Fossil. I used the original Wanderlodge Ross box and the Cummins/Freightliner gear driven pump with new hoses, and the big Freightliner reservoir with a new filter. When it had trouble turning at low RPM I attributed it to the extra 1000 ish pounds of weight on the front end, the oversize 315/80R22.5 tires I am now using, and the extra 4 degrees of castor I am running. But eventually I put a gauge on the pump and it would not do more than 500 psi. Should have checked that first, but now it steers beautifully.
I also need to redo my remote air operated clutch, which is just a light switch. No modulation at all. I used an air cylinder and attached a trailer hand brake valve to the clutch pedal thinking it would be a good way to have progressive air delivery. But instead it delivers air slowly at first, and then increasingly quickly so that just when you need less air you get all the air. So it operates backward. Not helped by the fact that somehow, I managed to get the shift pattern exactly backwards..... That was a head scratcher. I can run a lot of different shift patterns, but operating a 13 speed that is a mirror image of how it should be takes some concentration. I used the shift tower, cables and shifter from a Kenworth K100 cabover, and installed them pretty much the same...I thought. But something on those trucks must be flipped around. More research needed.
So, anyway, a couple days ago I went for a 30 minute drive. I was a tense knot of nerves with the new project stomach flu I always get, fully expecting something to blow up, fall off, leak out, catch fire, snap, bend, melt, seize, or just plain wind up dead in an intersection, but it was completely drama free. Never had that before from a project, ever. Not that I am done. I have a long list of things to do or redo next winter, including the fact that I have no engine brake, cruise control or temp gauge.
But it is a runner/driver and I am going to call it for now. But because I am an idiot and like to fail as publicly as possible, the second real trip for the repower will be tomorrow, with a load of passengers, and in front of screaming crowds. You heard it here first. Pics and report to follow tomorrow.