48 Frame Spa Pump Motor Shaft Thread Size

[SpaMon345]

I recently had to change out the wet end on one of my spa pumps.  First timer here.  The reason is the spa had been drained for about 5 months, and at some point the wet end began leaking onto the pump shaft, the shaft rusted and became enlarged.  I destroyed the old wet end forcing it off the motor. After using a wire brush and file on the motor shaft, the shaft had warn down considerably in the center, and became sort of bowed.  However the threads seemed ok, that is until I scuffed a couple of them up somehow.  

Putting on the impeller proved to be challenging.  It was extremely difficult to tighten sufficiently.  I eventually got it to not leak at the shaft seal.  I do not want to remove it again or it surely won't go back on as I am guessing that I have likely wrecked the brass threads of the impeller.

The next time it has to be replaced, though, I'd like to have an appropriate die available to chase the motor's threads.  I have spent likely over an hour and am unable to fully confirm the thread size of my motor.  The motor is:
Model: Emerson T55CXBMM-986
Flo-Master CP by Agua-flo
Model # 03621000-2
Code 06093

I "think" the size is "3/8-16 UNC 2A Right Hand"

Any and all insight is appreciated. Please and thank you.