Most SPF owners I know of that are running Mickey Thompson tires are running the S/T. Many others are running the Cooper Cobra tire. Both groups seem to be very satisfied with their choice.
I am very happy with my S/R choice, but as I said, I haven't put too many miles on them yet. My SPF was in the shop for awhile getting some repairs and upgrades, and she only came back home recently.
I am still sorting out some chassis and handling issues due to my high mileage (80k plus), effects of winter salt (several years but - no more!), and the car sitting for so long. Also getting used to my new (wilder) motor and trans setup. My next upgrade (hopefully a winter project this year) will probably be the R/T ball joints.
Cobra Valley's R/T Super High Performance Ball Joints
I am chasing a vibration in my SPF, and feel that the ball joint change should do the trick. Next spring I hope to start racking up the miles again, and should have a better feel for the Mickey Thompson S/R tires!