Bob -
According to my BFG specs, the 305/50x15 Euro T/A's have 27.1" OD, 12.4" section, and 10.3" tread on a 9.5" rim.
The 265's I have on front are: 25.5" OD, 10.9" sec, 8.6" tread on 8.5" rim. The 295 that a lot of guys run ilo the 305, is: 26.7"OD, 12.2" sec, 9.5" tread on 9.5" rim.
For reference, Vintage Blue Streaks are: 6.00-15 has 25.5"OD, 10.6" sec, 8.4" tread on 8.0" rim; 8.00-15 has 26.8"OD, 13.2" sec, 10.1" tread on 10.0" rim.
Then there are "Turk's tires" - the ones that REALLY make a Cobra look mean: Goodyear Sports Car Special T/A Rain: 9.00-15 (1906) has 24.9"OD, 10.9" sec, 8.6" tread on 8.5" rim; 10.0-15 (1907) has 26.8"OD, 13.0" sec, 10.2" tread on 10.0" rim.
Mort -
Get out there and DRIVE that thing! (whatsa' matter? too many choices? .....hmmm....GT?....427?...FIA?....must be nice!)
regards,
Jeff