I bought a 1969 GT6+ (US version of the Mk II) VIN KC50228L, new from Moomjean Triumph in Merced Ca when I was in the service. My first sports car
The Mk II model went to double jointed half shafts in the rear suspension with a lower A-arm, but still used the transverse leaf spring as the upper arm. Supposedly with a light weight car this was not considered a major design problem. With increasing emission control requirements lowering available horsepower, and economic problems, the Mk III models went back to swing axels as a cost saving to keep the car in production.
The GT6 engine block is the same as the TR 250 / TR6 block, but only 2.0 liters instead of 2.5. Don't remember if it was bore, stroke, or both different. The fuel system used Stromberg side draft carbs, with the sliding piston similar to the SU. Mk I cars were fully adjustable, but to comply with the first emission control requirements, Mk II and later had fixed main jets and VERY little adjustability. I believe all of the GT6 cars are 1974 and earlier, so retrofitting the Mk I carbs, or Weber DCOE's shouldn't be a legal problem in those areas affected by such things.
The only real problems I had that were not the results of my screw-ups were:
After I had the car about 6 months I went to the base car hobby shop to change the oil, and found the transmission was almost empty. I added about 80% of listed capacity of new fluid and never had to do that again so I think it was missed at the factory and at the dealer prep. Had to have trans bearings and bushings done at about a year and a half. Ther other problem was that the hood louvers were right over the distributor and rain water would make it hard to start. I got a rubber distributor cover (they used to make such things for British {and other} cars) and Kryloned the cover and wires into place.
I think about having another one now and then, but I have a 914 instead
Harvey