I have an 84 Bronco II with the exact same Motor. It takes about 15 minutes to do this repair. First off remove the air cleaner from atop the Carburetor. Next find the choke pulloff attached to the carburetor, It will be on the back left if you are facing the front of the truck. The hard part is trying to get a screwdriver or socket onto the screws that hold the pulloff to the carburetor since there is no easy way to see them. Just do it by feeling and take your time because the thing thats a pain is to drop the screws some where in the motor compartment. Once you have got those screws undone remove the vacuum line from the old choke pulloff and then install the new one in the reverse order. Now if you complete this and you still have this problem of stalling at low rpm it may be the carburetors accelerator pump.

All the choke pulloff really does is open the choke to a specified opening while the truck is cold. This allows the motor to suck in air from around the choke plate while the truck is cold. Since the pulloff is only opening the choke plate a certain amount this will cause the fuel mixture to be richer which is need on cold engine start up. Now as the motor warms up the the choke is gradually opened by the choke cap by an electrical pulse signal. Basically a coil of wire inside the cap is heated by an electrical current causing the choke to open as the wire is heated greater and greater.

So what Im trying to say through all that is that the choke pulloff really only matters when the truck is first started. Once it is at operating temperature and the choke has been fully opened by the choke cap the pulloff no longer matters. So if your truck is stalling after being driven for a while it wont be the choke pull off.

I had a very similar problem with my truck for about a year and only about 6 months ago found the problem. It had to do with the accelerator pump. So anyway my hand is getting tired from typing, so if the pulloff does not fix your problem. give me a shout back here and I can help you out.