I have a gear reduction starter in my TR6 but it has a high performance engine in it as well. These starters will make the car sound like a Toyota while its cranking just so you know. 
Before I ever got my gear reduction starter, I was once having problems with my original starter. It was dragging, really pulling the battery down every time I tried starting it etc... So I looked into rebuilding the starter. Turns out the bushings (driving end and commutator end) were pretty worn out and were actually beginning to bind the starter. I replaced these bushings and while I was in there I cleaned up everything else. When I put the starter back in the car, it spun so easily that the difference was quite amazing. After that, the car started much easier and used less battery in the process as well. Just something else to consider.

Shawn J. Loseke
Fort Collins, CO
http://www.triumphowners.com/79 (1972 TR6)
http://www.triumphowners.com/690 (1978 TR8)