I've also posted this in the slalom forum since I have interest in both....

Howdy, I bought an '06 XK8 in December. It's been a garage
queen for 2 months now (and probably will continue to be for
a few more weeks) but I'm starting to think about ''playing''
with it a bit.

I was wondering if you folks could give me some guidance on
wheels and tires for a bit of Autocrossing (Slalom?) and maybe a day
or two for an HPDE at a track.

I was wondering what offset ranges work?

Will the rear width wheel/tire work on the front?
(I was recently informed on a different forum that the rear wheels (19x9.5")/tires (255/40/19, would indeed work on the front, please advise if that doesn't match with the accepted knowledge)
Since rotating tires at the track usually
proves beneficial for tire life, and, obviously, all the
same size extends the rotation options.

I'm planning on sticking with stock size wheels, but buying a new set for just track/slalom.
Not sure if I'll do the 8.5" width or the 9.5" width if indeed the rear sizes work on the front.

Now tires?

Was thinking Toyo Proxes, or Falken 452, but then I read
about these Vredestein Ultrac Sessanta's..
Now a local shop has mentioned Hankook Ventus R-s3's.

What size tires available will also influence the wheel width I buy.