Just a little real world info about a 42RH behind your Magnum.

Or not behind a Magnum, whichever. :D

My car used to run at 2,800 RPM's at 80mph.
With the 42RH (A500) overdrive with converter lockup the RPM's at 80 are now 1,800
Took it out today and tested it on the open hiway

1,000 RPM decrease in RPM's on the freeway.