I have no hope of getting one of these trans, so I'm seriously looking into this:

https://shiftsst.com/articles/cat/mopar/post/challenger-barracuda-1970-1974-perfectfit-kit/



Tremec T56 Magnum Kit Components

Tremec T56 Magnum 6 Speed Double Overdrive

PerfectFit Shifter position fits inside the factory console

700 torque capacity wide or close ratio.

Friction Lined Synchronizer Blocker Rings come standard for easy high RPM shifts

Full 12 month warranty with unlimited technical support, 24 month installation window

Optional Add the Front Shift Kit for bench seat clearance

SFI Rated Steel Bellhousing

Hydraulic Clutch Actuator Kit

6-Speed Pattern Shift Handle Insert

Sheetmetal to widen tunnel

Speedometer Connection

Mechanical and electronic compatible
Speedo Gear

Reverse Light Connector

Pilot Bearing

Super heavy duty needle roller type with lube seal for long life

Crossmember - No need to replace torsion bar suspension. Stronger than the original equipment crossmember.

Isolator Mount

Rubber for vibration isolation

Installation Hardware

Slip Yoke and Driveshaft

Detailed Installation Instructions - including free lifetime tech support

12 Month Product Warranty

Includes 24 month activation delay so you can finish your project.