As spec said, without knowing the rim width we can't say what size you can run.
However, based on the sizes you posted, you can't run your tires on his rims in case that is what you were asking (kinda sounded that way).
If the Saleens are 18x8" rims, then you should run a 245 tire. If they are 18x9 then you should run a 275 tire (265 minimum).
Once we know the actual size of the rims, we can tell you the proper tire size to use. :beer:
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2.2L KB Supercharger, 4#, Billetflow Single Blade TB, JLT Carbon Fiber RAI, Nazty Performance Ported Lower Intake, Bassani Midlength Headers, O/R H-Pipe, Borla Stinger Catback, Tuned by
RWTD --- Numbers coming soon...