Got hit hard in rear end.but driveable can i run 1 size larger tires on the front

If you are running one odd tire, you will be ok. IF you are running a PAIR of different size tires, mount them diagonal from eachother.

 

OR, if you run them in the front, (assuming automatic) use the FWD fuse and limit your driving until you get matching wheels. for manual trans mount them diagonal

no you can't do what you said. 

1. use the FWD fuse

or

2. milesfox has another option which shops around here use for installing two new tires on a subaru.

 

if it has a rear locking VLSD differential then you can't have mismatched tires on the rear though so option #2 won't work without frying your rear diff.

Same size tires but fronts are tall rear.now code on dash torkconverter circuit