I talked to Coker. They advised the 525/550-17 stock tires. I was hoping someone out there had luck mounting something bigger. I think the rim are 3.50 wide. I do not know how much over the width of the rim you can go and still be safe.
The biggest Firestones Coker sells for 17's is 600/650. I just mounted a pair on 17 inch wires, no problem. I haven't driven on them yet but I can't see why they wouldn't work.
I have a set of the same wheels going on my track roadster and I'm running 5.50's on the fronts and 7.50's on the rears. Chris has the same setup on his AV8 roadster.