widest tire with tail pipes?

[woodyy24]

anyone know the widest tire that will fit without hitting the tailpipes?
its on an 85 GT. with 2.5'' tails. and i just bought a set of 17x8 96 cobra rims(4-lug).
i was wondering what size i should go for. i was thinking p245.45.R17s.
right now i have P235.60.R15s on the back and theres a bit of space left.
just wondering whats the biggest i can get under there.

 

[Rick 91GT]

I have a customers 88 that has those exact wheels with a 245/45/17 and it is as wide as I would go, just barely clears the tail pipes

 

[woodyy24]

ok thanks