A Body Stalling at Idle

I'm betting it isnt outright converter failure, otherwise you would have to use more than just a little "flutter" of the gas to keep it alive, it would pull against the brakes really bad, and you would have notable "engine braking" while slowing down. In short, the car woudl drive totally different. Not bashing your shop, but it sounds like they are trying to "sell" you a new transmission. And their grasp of Torqueflites is dubious. If you had a TH700R4 I might believe the converter bit. Unless you are running a mid 80's or later transmission, there is no way anybody "accidently" installed the wrong converter. Sorry, won't fit. Wouldn't have worked fine for a while either.

I agree with 65Val's suggestion of taking vacuum readings at idle both in gear and in neutral. Here's what might be happening... With the car in gear idle speed drops and vacuum may be dropping to the point where the metering rods try to rise. This causes the primary circuit to go rich, and idle will suffer. Easy way to check this would be to pull the metering rod covers and watch what happens when you pit it in gear. If the needles try to rise, you dont have enough vacuum at idle to keep them down. But since you say it was running great before I am guessing your basic combo works and there is something minor wrong. Carbs, especially new ones don't just break.

Do you have power brakes? Replace the PCV lately? Start out by removing all vacuum load from the engine. Remove the booster line at the manifold and cap the port, same with the PCV line. Make any difference? If so one of the two is leaking. Hook one back up and try it, that should help you narrow it down. Another quick way to check the brake booster would be to set the parking brake and put it in gear and see if it still wants to die. How about if you stomp the brakes 2 or 3 times in neutral?

You suspect an intake leak, and it certainly possible that one or more ports is sucking air from the lifter valley. To check this you need to allow the crankcase to build vacuum. Cover the breather (opposite valve cover from the PCV) with the engine at idle. Use your hand so you can feel the vacuum build. If the idle speed changes at all, you have a bad intake gasket or PCV valve (but we already checked that).

Another thing that will cause the engine to die when coming up to a light would be too much timing advance, caused by a sticking mechanical advance, too much initial timing, or vacuum advance operating at idle. You said that the shop did something to your distributor. Trust but verify, in fact it sounds like they sold you a coil in trying to fix this. Coils dont cause this. If it starts, the coil ain't it. Hearing this as well as hearing that they "blew out the carb with an air hose" and "rebuilt the distributor" makes me cringe. In fact I get a real bad vibe.

I'd take a look at your base timing. Should be no more than 5-10 degrees BTDC. Make sure the vacuum advance is not getting vacuum at idle by disconnecting the hose at the distributor and verifying that there is NO vacuum. Plug with a golf tee and leave disconnected for now. Now shine the timing light on the marks again and slowly rev the engine up to 2500 rpm or so and let it drop back to idle. The timing mark will advance out of view and should return back to where it was as soon as the engine returns to idle rpm. This indicates the mechanical advance is working.

If the above checks reveal nothing, then and only then might I suspect the transmission. If possible, make these checks yourself and/or have a local forum member help you. I am guessing that you have already handed a significant amount of money to that shop and they still have no clue. Don't take it back there. Remember shops aren't in business to fix cars, they are in business to make money. Are they willing to do the transmission for free if it turns out no to be the problem?