I've run 245/50/15 with 4.5 backspacing with converted small bolt pattern axles which are 3/16" narrower than 4.5 backspacing aftermarket axles. I've also run 15x7 rims with 4.25" backspacing 225/60/15 tires and also 235/60/15 tires on same rims without a problem.
Now in the front, you could be pushing things close. Be very alert and cautious of the front bottom corner of the fender lip. Having the car aligned to 3+ plus caster will help clearance and will help the car feel like it's handing better and take away a little of the super overboosted power steering feel.