It's an old post but others probably have had the same problem so I'll post this. Buy a cheap vacuum-fuel pressure tester from the parts store. The engine vacuum test can tell you if it's a plugged cat. or exhaust, late ignition timing, sticking valves or other problems. And by testing fuel pressure and flow rate you'll know if you need new lines or pump. But most likely it's the Quadrajet carb. Remove the stock fuel filter which clogs up easily and replace it with an inline filter( if you cut the fuel line a few inches away from the carb. it will be easier to remove the old filter. And the new filter can be installed where you cut the line) . Try holding the choke open by tying it, or even by putting a screw driver down the carb. , take it for a test drive and you'll see it stopped stalling up hill. It's better to buy a new carb. either Q-jet, Holley, or Edelbrock unless you have the Rochester Carbs book and some experience. A hand held vacuum pump can be used to test the choke pull off (as well as the EGR valve and the vacuum advance canister on the distributor), and new electric choke coils aren't expensive. But the old Q-jets have a habbit of leaking internally and emissions carbs have sealed mixture screws which make it hard to fix with out removing and rebuilding it. Some mid 70's to early 80's Q-jets were known to have porous castings which would leak and aren't rebuildable and the computer controlled Q-jets are junk.
