will a 4-speed transmission from a 1991 f-150 with a 302engine, fit into a 69 ranchero with a 302??

The transmission, yes, will bolt up to the engine/bell housing. The problem is the transmission mounts are going to be in a different place on the Ranchero, different wheelbase and you will probably have to have your driveshaft shortened or lengthened to fit, there are shops that specialize in that, they can cut, weld and balance your driveshaft and hopefully the splines will match. If not, the right splines can be put on it. Then there is the matter of linkage, if the shifter lines up with the hole in the floorboard of the Ranchero...that can be dealt with too, there is always a way