I don't think the legroom changed much over the TR series up to the 7, the TR3 was the same as the 2, the TR4 built on a widened TR3 chassis, the 4A got a new chassis on the same body and cockpit, the TR6 had the same frame and cockpit as the 4a/250, maybe some difference in the seats or seat adjustments.
I ( average size, 6' 210) find the leg and headroom in my TR250 (same as a TR6) more than adequate, and don't even have the seat all the way back. They are a bit narrow, which you feel a lot more when you have a guy sitting next to you in the car.
My first car was an Austin Healey Sprite, so I am acclimated to small, I think if you mostly drive big american cars or SUVs any LBC is quite a shock.
I have also had MGBs and a Healey 100. The TR is best for space, the MGB has good legroom, about the same as the TR and is a little wider, but has less headroom, the 100 is tighter on legroom, and very tight on headroom with the top up (my head brushed the top), the midget is of course tighter all around.
In addition to a smaller stearing wheel, some reupholstered seats get overstuffed, and cutting some foam out of the back or seat can help. Never owned a Jensen Healey or TR7, but have driven them, they are indeed both very spacious in the cockpit.