Triumph Repair: Trying to find what gearboxes I have, triumph spitfire, spitfire 1500

Question
I have 2 gearboxes--one that's in my 1980 Spitfire 1500, and one I bought off eBay that was described as from a late model Sppitfire. I can't verify if the one in the car is original. The gear cases are identical, but there are different numbers of teeth on the gears. According to Victoria British, the gearboxes are very similar (many part #s match) on the MG Midget, Triumph Spitfire, and TR7. It is difficult to know what parts to order. Is there any way to know which is which from numbers or markings on the gear case, rear housing, or any other method?

Answer
Hi Tom,
It has been many years since I worked in BLM dealerships but as I remember there were different gear teeth configurations and as I remember we always had to take the part number off of the lay gear to ID the gear set. There should be a part number on the lay gear so try to check with the suppliers like Victoria British and others like Moss Motors, The Roadster Factory and Engel Imports to see what they apply that lay gear to.
Howard