The fronts aren't really a problem, but for the rears there's good news and bad news. We share the 255 - 50 / 16 with Mustangs and Corvettes which should mean tyres are plentiful - but they are not. Their US and UK forums all have topics on the problem of tyre availability. The bad news is, we also share the tyre size with a few Aston Martin and Ferrari models so you just know it isn't going to be a budget solution.
I have been running Khumos all round for the last 16,000 miles and they have been great, but Khumo have now stopped making the 255 - 50 / 16. I have contacted Khumo in the UK to see if they have any left in a corner of the warehouse and they don't. As a back-up, yesterday I bought a pair via EBay which must be the last Khumo 255-50 in the UK. I've searched the internet and also contacted
www.micheldever.co.uk in Hampshire as they are recommended on the Mustang and Corvette forums and they have a few sets of the BF Goodrich in "our" size at a reasonable price.
I also contacted Longstone Tyres who were very helpful and told me Michelin have recently re-issued the Pilot Sport in their Classic range, but at £ 400 + VAT each for the 255 - 50 / 16 it's a tad expensive
http://www.longstonetyres.co.uk//page/5756.
Currently, I'm talking with Khumo to see if they have a road legal track tyre and will let you know how I get on.
All the best - John.