I have one in a 66 GS behind a 401, I have 2.92 posi gears in the back. To use the s/p you need tall gears, some where in the high 2.00's, that way you have a s/p 1st gear to get started. Remember the 400 uses HP to operate.
Diver
My car was one of the first TR's with the SP. The first time I took it out for a spin, it took off like a raped ape. I could feel the difference. Think of it. You power brake, you activate the SP to flash at 4000 via brake switch. I have the timer installed as well. The hi stall will get you up to boost quickly, then when you go to the low stall (1500) all the power is at the ground. I usually have my timer set for 1.5 - 2 sec. I put it to 4k for 10 sec once and couldnt control the car. It was all over the place.