TurboCoupe Rear-end...How BIG of a Tire can fit ??

[Katmandu]

I'll be installing a TurboCoupe rear-end in my 89 5.0 in the next week or so. Given the fact that the TurboCoupe's axles are 3/4" longer will make the rearend 1.5" wider than the Stock rear-end...

I need to find out what is the largest tire (15") that will fit underneath ??

What have you'all experienced with this set up ??