it sounds like your idle has to be adjusted...there is a possibility that you got some kind of moisture in your fuel system, or some sort of dirt in your carb, a cheap way to check that is simply stop at a gas station before you fill your tank again and add in some dry gas...see how that runs....they also make injector cleaner for the tank, idealy if you believe the gas is being cut off more so then the truck just stalling out from bad adjustment, you could try a fuel pressure gauge to rule out a faulty fuel pump

a good way to kind of see what is going on, pull your spark plugs and take a look at what kind of wear you have on them...maybe clean them up a little bit, i know if you were playing with the timing you could have fouled them up a little bit too

try sitting under the hood and working the throttle, listen to the engine as you rev it up and slowly let off, see if you can hear it start to miss at all as you bring it down to idle....

did you try to adjust the air/fuel ratio at all...there should be a little screw adjusters on the carb, but you probably have to drill that plate out to have access to your idle adjuster...as big of a pain in the a@@ as that may be...