Quit messing around with so many different ideas and settings.
Spark plugs will not make it run funny, they will cause a miss. As long as they fire and don't miss, leave them. Heat range is the only difference, cold or hot, if you are running rich, go hot to keep the tips cleaner.
Timing will not make it run funny on one carb but not the other so leave it alone. If it starts and idles, its fine.
Distributor 180 out, very doubtful, easy enough to check if you want. Pull number 1 plug, crank till you feel compression at the plug hole, look at rotor to see that its pointing at or close to #1 plug.
Fuel pumps will normally only effect high speed or acceleration driving. It would have to be pretty bad not to supply enough fuel to idle. When they go bad, the engines go lean or fill the crankcase with fuel, sometimes both. From what I have seen, over rich carbs turn the oil black and fuel smelling. Bad fuel pumps thin the oil but not change it's color much, no carbon deposits washing past the rings.
The reason it runs on one is due to the fact the other carb is still feeding fuel through the idle circuits and possibly flooding over. Pull it clear off and block the intake, and your other carb will not feel so good.
Whats this leave you with? one bad carb. Just pull it apart and give it a good cleaning, set the float after checking it for fuel soak, and give it a try. If Tom is a decent seller, which I believe he is, he won't mind if it saves you and him shipping cost. You also have this thread to prove you tried everything before going into the carb.
Try this tip from another thread here on the board. Loosen the hold down nuts on the good working carb and raise it enough to slip a piece of aluminum can under to block the air flow to the manifold then tighten it back down. Now the truck should only be running on the front carb ( dirty one ). Speed up the idle to 1000 or 1500 and with one quick move slap your hand over the inlet to choke the engine down and force lots of fuel down the engine. Don't let it die, clear it out with more rpm and do it again. This just may be enough to force out any crude in the jets. My tri-carb set up would routinely stumble and load up if I drove it easy all the time. About once a month, I would have to run it full rpm to keep them cleared out. I never could figure out why, I just new that when it started to shake at idle, it was time to hit the on ramp for a full throttle blast. Yours sounds just like mine did.
Joe
