Thermo quad bogging badly when stomped on

Dancin,
Because this happened 'suddenly', it is a back to basics job.
Check that the choke blade is fully off & linkages across the top of the carb are free & working.
I doubt it is acc pump shot, but could be. Easy to check. Run the engine & switch it off. Remove A/C & while looking into the pri bores, actuate the throttle lever. You should see a squirt of fuel from the acc pump nozzle into the pri bores.
No squirt means an acc pump problem. Plunger worn out, valve problem, link hose off. Needs a new kit.

Secondary operation. Any binding here will cause a very rich condition & a bog. A rich bog usually has a blubbery feel about it, hard to explain, but different than a lean bog. When these carbs get old, the sec air valve [ right rear of carb ] rubber diaphragm in the AV goes hard. This prevents the AV from opening, acts like a choke & you get a rich bog. To test: while watching the diaphragm, start the engine. Plunger should pull in. If not, dia is faulty, or rubber hose is leaking, etc.
If dia pulls in ok, switch off the engine. Gently push in the dia actuator with a flat blade screwdriver & then let go. The actuator should release smartly. If it is sluggish, dia rubber has gone hard.

If all of the above checks out ok, I would get a rebuild kit for the carb & rebuild it, especially it has a lot or unknown miles on it.