One of the things of concern for the future is the 50 year old trans shifts too low, even though I'd adjusted the kickdown to the FSM procedure (same as this cute one https://www.youtube.com/watch?v=KsfI9cFFPpg) when I did the bands oil and filter. Just guessing, but the pressure might be a little low with old seals and worn parts. At WOT it goes 1-2 and 2-3 at about 3000 rpm, and actually does not kick down very easily. I've also noted that on the flat it starts out in second unless full throttle (I can shift the lever and it drops).
If anyone knows or has a source for proper values at the outside tap ports I would check them.
Any other test suggestions are welcome.
It is hard to gauge shift behavior of a 11,000 lb rig, but it seems smooth without hesitation or clunks etc. My B3500 is firmer, but had a shift kit and only weight 5,400.

This is part of my impetus for the other OD thread; if it has to come out, what to do?

If it doesn't start out in 1st gear the governor weight may be sticking.

I think it is in first with heavy throttle from a stop. I'll have to check when weather lets up.

Starting out in 2nd can be a governor or shift valve problem.

At a standstill in Drive, the governor pressure should be less than 2 psi and will be roughly 1 psi for every mph when rolling, depending on the axle ratio and governor configuration. Too high governor pressure at a standstill will prevent downshifting to 1st at a stop. If the pressure is 2 psi or less and it doesn't downshift to 1st, it's most likely a sticky shift valve in the VB.

The factory linkage adjustment can be tweaked (lengthen the linkage) to make the trans upshift later at light throttle and make the forced downshift come in quicker. Also be sure that the carb is actually at WOT with the pedal on the floor i.e. have somebody sit in the vehicle and floor the throttle then, from under the hood, push back on the carb lever to see if it's wide open.

Is there a port for governor pressure?
EDIT: aha, I see https://www.youtube.com/watch?v=64jGAok7CqY and https://www.youtube.com/watch?v=BqZtpjfczgo

The linkage on the RV is easy since one can see the whole thing from the driver's seat. I'll check again and maybe add one twist.
I thought I'd read that too much linkage length can cause different issues as well.