Stein, that duplicates my experiences, too.
There seems to be more early 70's Triumphs here than any other years and because of that, I've done more work on those bikes than others in the last few years.
Of course, I get to test ride them all!
71-72 TR6's and Bonnies run the best of all the bikes I've ridden. To qualify that, I like the torque spread, throttle response and top speed the most of all the Triumphs I've ridden.
Looking at the bikes with a critical eye, the heads bear witness to this. Everything else seems to be the same as other years.
So, If I were to have a unit bike, I would copy the specs of the 71-72 TR6 including the head specs. A 750 kit is not out of the question either. It's all about the fun factor for me.