I've had the Goodparts diff in my 71 tr6 now for over a year, and really like it. It was as easy to install as the original, came with all the hardware. I also ordered the new driveshaft. Fit an finish of the adaptor plates is very good.
Compared with the sloppy diff I took out of the car, the Goodparts conversion really tightened things up. It's a very quiet diff.
I autox the car, and this LSD conversion is the missing link to outstanding performance in a TR6. I've got two seasons of local competition now with the LSD and all is well. I'll post a pic of my car.
All said, I would highly recommend this conversion, it's money well spent.
HTH,
Kevin