Are there any real differences in the headlight switches between a '77 Dodge Van/Motorhome and a 70's A body other than the handle you pull out. I am doing some work on my neighbors motorhome and the dashlights don't work too good as you try to adjust them. They only work at the dimmest setting or intermittently as you turn them up. Actually you have to wiggle the handle to get them to flicker. I have a few spare A body ones and was wondering if I could use one in the motorhome and just use the pull handle that is currently in it with the A body switch.

Sounds like you could just clean the coil and the sweep on the switch you have to make it work.

Try some real fine crocus cloth, or 2000 grit wet and dry sandpaper You want to use it enough to burnish the corrosion off, not sand thru the contacts

i discovered that you can use a 76 newyorker headlite switch on a 64 belvedere. plugs right in and you can use the 64 switch knob. you also gain the parklite on with the headlites feature. i would say the dart switch would interchange with the motorhome one. but as was mentioned, it's probably just corrosion on the dimmer reostat.

Another suggestion..
Jumper the dimmer rheostadt, its voltage drop is minimum so run the dash lites at a full 12V. They aren't that brite to begin with.
Pull the 3 pin connector and jumper the 2 orange leads (I think at least the cars are orange) with a short lead and terminals.

Just my $0.01..