The Saganaw SM326/BW R10Q is a better unit but was only used for 4 years so there are not many around and are priced accordingly.
They also have some unique differences, one of a kind solenoid and governor, different side cover configuration, and fine spline output shaft.
Fred


1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine