Check the archives in the Corner Carvers section. I highly recommend the ROH 16x8 with 245-45 or 245-50 tires. The 255-50's will be too "tall" to fit in the wheel well.
I personally ran both the 245-50's weee bit too tall, then went to 245-45's (short) but fit great.
Check out the photos of my car with them on it:
Mustang wheels and tires
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Darius Rudis
Home built t-arm/panhard suspension powered by an S-trimmed motor :-)
My Mustang Page