I personally like the Goodyear SC3R 305/325 you are looking to run! They seem to be very consistent with laps with loads of grips! I did have to run more tire pressure than expected, 40/41 psi front and 36/37 psi rear Hot! I was also running -3 F/-1.6R camber for reference!
Just and FYI, if this TSB doesn't work. I also did a small write up on how to replace the tone ring and PN# as well.
https://www.mustang6g.com/forums/threads/rare-problem-5th-6th-gear-bucking-surging-and-cruise-control-not-working.125235/page-6
I have a full set of Project 6GR 7 spoke gloss black R spec wheels for sale. Fronts. 19x11 rears 19x11.5. These have roughly 500 miles on them, found my dream set of Forgelines so, these are up for sale. One of the front wheels had a few small chips from mounting. 1100 bucks, new these are over...
This is my rear poke on a good year SC3r on R spec P6GR wheels! If you run a Michelin PS4 325/30/19 they run really wide! With a 11” rear i wouldn’t run more than 315, 325 might give you to much bulge.