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

I'd sure like one of those in mine

Del, I got mine out of the U pick it for $150 w/lockup converter out of a 2 wheel drive 1995 Dodge Dakota that had both fenders and the hood crunched.
I figured the front end damage took it off the road and not a drivetrain failure, so the chances of a good trans was better.