as i suggested
there is another adjustment that is hidden behind a small plug
standing on that side of the truck looking at the mixer if you look at the right side of the mixer you will see a small round projection in the casting at the base of the mixer bowl that will have a plug in it inside a small hole about 1/4 in in diameter. That plug has to be removed so you can get to the dwell adjustment screw.
You will need the MCFA Diagnostic software on a laptop and the cable used to connect to the ecm so you can correctly setup the system.
From your description of the symptoms this is what is wrong
turning the idle/air mixture screw will not accomplish what you need. I could be wrong but i doubt changing the converter/regulator will change anything much either. Unless it is freezing up, truck is running like crap stumbling on itself or leaking lp gas the converter/regulator is probably ok.

Up to you though...