

If you can see this picture (Im not good at uploading tags) look at the small green disk next to the choke housing, between the choke housing and the carb body. Thats the high speed idle cam. One part of it is wider as it turns, so it pushes out against a screw. That gives it the high speed idle for when its cold and once the choke opens, and you press the gas pedal to the floor, that green disk should drop out the wide part isnt under the screw and doesnt push out anymore, letting the idle speed drop.
If thats the problem you could just screw out the screw a turn or two. It shouldnt make your idle go up drastically all of a sudden so I think its something else.
Look at the back of the carb behind the valve cover the firewall side. See if you the spring in this picture.


That pulls the throttle shut and the cable to the pedal opens it. If that spring came off that would cause the throttle to be open maybe.
You might even have a vacuum leak look at all the vacuum hose and make sure none of them came off, try pinching them shut one at a time with your fingers while the engine is running. If you pinch one shut and the idle drops theres the problem. My old 74 had a leaky vacuum canister that caused a vacuum leak and made it idle too fast. Its just a tin can with hoses going in and out, but I guess the seams started leaking in air, and it acted like an extra carb to let air in and raise the engine speed.
Let us know what you find.