I dont have the Rallys your discussing but I do run 18x8 4.5"Bs rims on front and back of my 71" dart (which is a 0 offset if rim sizes confuse anyone). There is a little bit of room in the rear to the spring but I dont know if I could get any closer with the limited BS options. The rear to the fender is as tight as it could be. I cant get my fat finger between the two. The front could in my opninion come in a little bit but with the 4.5"BS I do not have any rubbing to the fender. My car is lower than most I see, and I run a front swarbar now which allowed me to lower the car another 1/2" more than what is the picture below.
This is before I installed my swarbar and lowered it a little more.