The u joints on both my '37 and '42 are the type that cannot be disassembled on the truck. Thus, to drop the torque tube to remove the tranny you must remove the u bolts on the rear axle and using a long pry bar move the rear axle back about 6 inches (or as far as the flexible rear brake line will go). Also, unhook the parking brake. Then you are good to go. With a lift this is not all that difficult especially if you have help.
Regarding your extra tranny, I don't recognize the casting number so maybe it is a three speed? If so, it will be synchronized in 2nd and 3rd. The present tranny is definitely a 4 speed, non-synchronized.
In addition to shift rail problems, like stuck indent ball/spring, there is a soft metal shifter guide riveted to the underside of the shift tower. That part wears and may be the source of your problem, especially since you are able to put the tranny back into neutral. Just take the top 6 bolts off and take a look. If there is wear you might help by filing the guide to a smoother contour. The manual says to drill out the rivets and replace but I have never seen one come up for sale. You can take the shift tower off in the truck, after you remove the floor pan. Maybe start there in case you get lucky and that is the problem.
Kent
