back up light switch....help!!!!!!

[wade]

i have a very confusing issue with my 72 gmc 1500 regarding the back up light switch. my problem is that the switch itself works fine,but it leaks. So no problem, just replace the switch. my issue now begins, it seems that this switch, according to over 4 parts stores and 3 transmission shops does not exist on the thm 350 transmission. I know for a fact that this is the back up light switch, because unplug switch, reverse lights dont work, plug switch back in, lights work. the switch i speak of is located right in front of the dipstick tube on the passenger side,and aft of the detent or kickdown cable. most other thm 350 that i have looked at either have this port pluged off, or on later transmissions,this
was the place they put the lock up torque converter switch. my question is how can this be!!!!! did gm come up with different reverse switches for different years, when i have ordered the so called switch from a parts store, they keep giving me the neutral safety switch that goes on the steering column. and how can the same port on the same thm 350 transmission be used for a back light switch on one and a lock up converter on the other, i wasnt even aware that the thm 350 ever had a lock up converter mated with it. so is this some wierd hatch job that exists on my tuck only
or does anyone else out there know of what i speak????