Currently putting together a 1966 727. More HD than race, the Super Sprag and Billet drum are out of the budget.
Changes so far have been replacing the 19-spline input shaft with a 24-spline input shaft so torque converter choice is easier. Rear vent, and sprag lube hole from the cooler return. Threaded restrictor plug in case. FT-2 Shift Kit using the stock '66 servos, stock 3.8:1 band lever.
Have an old rebuild kit where all the clutches were supposed to be Alto red eagles, but bulkpart shipped alto read eagle rear clutches and Raybestos Green (High Energy) front clutches. Kolene steels for both clutch packs.
The trans looked pretty good and stock with maybe one rebuild (low mileage car.) No stripped threads in the case, sprag still tight in the case, but previous rebuilder had many of the sprag roller springs installed backwards. Might install a later dual "O"-ring rear band pin.
Haven't decided on bands yet. The stock bands look fine and thinking of reusing them, but I have a new Mopar Performance Front band on the shelf. I think it is Kevlar? Not sure if I should install it or not.
Need to still get a trans cooler and maybe a deep pan.