Saginaw trans was developed for four and six cylinder cars. The trans was available with several different gearsets. These are all wide ratio gear spreads. Most have too low first gear and a big drop in rpm going into high. I have seen four cylinder Vegas break them on a good traction drag strip.
Borg-Warner T-10 and Super T-10 were made by Warner gear. The first series was used from the late fifties till the mid sixties. They shift very smoothly and can take moderate horsepower. Several gearsets were available.
Muncie was introduced by GM in the late sixties as a replacement for the Borg. Muncie trans can take a bit more horsepower than an early Borg-Warner but are not as smooth shifting. M-20 had a low gear ratio of 2.52 or 2.54. M-21 were considered close ratio with a 2.20 low gear and less rpm drop between gears when shifted. M-22 was a heavy duty version of the M-21. The gears were cut at a different helix angle to make them tougher. These gained a reputation as "noisy" . They whined thru the gears.
The Borg-Warner Super T-10 is the best of the OEM 70's supercar type four speeds. It was introduced in the early seventies. It was available with many different gearsets and was good for lots of horsepower and sticky tires.. It is still available thru Richmond gear..