Not an expert, but I believe the "PowerShift II" was on 1973 and later..
1972, if I'm not mistaken, is Hydro-Electric shift in which case you need Premium Blend or Type "C" lower gear oil. Not all Type "C"'s at the same though I've heard, so be sure it's specifically for Electric Shift.
If indeed you have "PowerShift II" I think the engine would be a 1973 or later, which is hydraulically assisted manual shifting (not electric) then I still think you need premium or Type "C", but doesn't have to be specifically for electric shift.
If your model number you posted is accurate, then pretty sure you have Hydro-Electric shift, and maybe the remote is a PowerShift II type that was rigged to work...
Do you have shift buttons or anything for shifting the gears?
EDIT: Found model numbers 50ESL73R, 50ESL72C, but can't find a 50ESL72R.....
Could you double check your model number?... Just in case?? LOL