My understanding was the previous owner spent 2500 for the rear and 800 on the driveshaft.
One can do the 9 inch for less.. The housing/tq arm bracket/and axles are approx 1000. You can buy a center section on ebay for like 350-500 with a Posi 3.25 gear. Using the stick brakes that are on the TTA.
Depends on how much time one has and is willing to figure it out.
My old TTA still runs the 9 bolt. Tonite that car ran 11.030 at 123 driven to the track and back home..
Mine sat home taking a break for next week.
If you keep the 60 foot in the 1.6 or slower.. that 9 bolt will live a very very long time.