42RH / A-500 in a Duster with pictures.

If you use a nitrous fuel safety cut off switch some adjust between 30 and 70lbs/mph.
I have my A500 set up to use the governor pressure port to activate the solenoids at set speeds for OD and lockup.
The OD comes on fully automatically at 55 and lockup at 65 with these switches, and I ran the line up the back of the trans and bolted the switches on a bracket to the rear of the intake so I can get to them easily from under the hood for speed adjustments.

I did install manual switches on my shifter base to override OD and/or lockup if I prefer. (for heavy throttle applications) :D
The trans is designed where OD will only come on after the trans is already in third, so for example if I have OD turned off manually the lockup function will still activate at my set speed (65) but the trans would still be in third instead of OD.
This would make it shift 1-2-3-lockup@65.
If lockup is manually disabled it shifts 1-2-3-OD@55 only (no lockup)
With both switches in the "Auto" position it shifts 1-2-3-OD@55-lockup@65
With both switches in the off position it shifts 1-2-3 like a 904, but with the low 1st gear ratio of the A500.

This also requires the 80 inch speedo cable, so be ready for that. :D
Oh, and A500 cooler lines are 3/8 instead of 5/16 like the 904/727 but the fittings on the case can be changed if needed.
What I did was change the cooler lines to 3/8, as well as the fittings on the radiator and found them easily at Ace Hardware.

ShifterArt.jpg