OK. I wanted post a few thoughts that may or may not be interesting/relevant.
The truck overall did better than I expected. It's not a quick accelerator, but once up to speed it tugs along just fine. Much of the interstate we ran 70mph at 2000 rpm in 5th gear, downshifting as needed on steeper inclines.
I need to do the hydroboost brake conversion. My '86 had it and it was much better at stopping a load. At a gross weight just over 20k the stock brakes really don't quite cut it.
The ZF5 made it ok, but this would have been a nightmare coming down some of these passes with the automatic. The ZF5 really shined when we could downshift and use the IDI 'jake" sounding braking down the steeper stuff.
Fuel economy was about what I expected. The worst tank was high speed interstate and came in at 8.56 MPG and the best tank was 9.77 MPG on the slower winding backroads. Overall MPG was 9.18 MPG over about 1657 miles.
The intercooler worked well, but how well I cannot quantify as the gauges didn't work out for this trip. I would really like to do back to back testing against an Air/Air IC just to see how they stack up against each other. There were never any indications of heat soak or anything like that.
My fuel is turned up just enough that I would hit 1250 F EGT as I crested most hills with the throttle on the floor and ambient below about 80F. Above 80F I was having to lift slightly to get the EGTs down under 1250.
Thanks for riding along!