Doubt that many of the pub dwellers in Conventry would appreciate the Irish jig, but I will try to help.
I seriously doubt if you will find any of the "original field test" data in an accessible format. Perhaps British Motor Heritage? However, Brooklands Books published an assortment of comparison tests from Road & Track, Autocar, Autosport and other car mags in the early 80's. It was titled "TRIUMPH TR6 1969-1976". (ISBN 0 907 073 59X) Have no idea if still in print or available. Try Motorbooks International?
As for factory specifications, if you can get a copy of the the original "Repair Operation Manual" (part # AKM3529) you will find everything you want. Otherwise obtain a copy of Robert Bentley's "Complete Official Triumph TR6 & TR250 1967 - 1976" (ISBN 0 8376 0108 8). This includes reprints of the Drivers Handbook and the original Repair Operation Manual mentioned above. The major difference between the factory book and Bentley is cost and availability, Bently is still in print.
Enjoy the restoration journey, it is very rewarding and gratifying.