I've got front 245-40-17 on 8" (0 offset) wheels. Front is lowered, and there is more than 3/16 clearance to the fender lip. I'll measure it tonight if you need. Also the 40 series is a tad wider then the 45 series, so you should be fine for that size.

Nitto 450 has a 275-50-15 but the front would be 225 or 255 50's. At one time I was thinking of switching to those. I have the 315-35-17 on the back now,

I can tell you the ride is pretty stiff with the tires I have. Your choise of 275-40-17 and 245-45-17 isnt going to be much different than what I have.