okay Brad..that really does look sweet!
..the RN73 was a 370 and not a reed motor
I reckon a 'closer to the '73 RA125 spec motor' would be the '75 M or S
The S was basically a factory kitted M.
Not arguing anything and on looks alone then yes, I agree, the RM125A looks more like the RN73 than an S or M motor but then so does the B and the bigger finned C motor and these may be easier to find
grind off the numbers and not many could tell the difference between the A B and C.