The Muncie is weak in comparison to the New Process 833.

It would seriously devaluate your Charger too.

As said, used 833's are not expensive. What is expensive is the non-muscle era gears, meaning mid-70's and into the 80's. Get an 833 that is a 68-70, repro gears are cheaper than NOS.

I just rebuilt a 73 A-body trans and went through all that cost myself.

The 833 is very easy to build too. You just need good snap-ring pliers and a home-made countershaft arbor for loading the countershaft.

Forget the Muncie, Chevy racers did and they used to convert to the 833 before getting away from manual trannys altogether.