I was wondering what other Regal guys use for aftermarket rims on the back. I measured the stock 14 inch rims and they are 3.5" back spacing. I talked to a guy who has been around some Monte SS's and he said an 7 or 8" rim with 4" back spacing works with 275/65R15 tires. This is with the stock rear end.
I tried a 8" wheel w/4.5 and it didn't work w 275/60 - 15 tire and was off by at least 1/4 to 3/8". 4" back space should work, but be real tight. When cornering or hard acceleration, may hit frame. I had the frame notched a bit.
Many G body owners go with 235/60r15 in front and 255/60r15 in rear with no issues at all. I've seen a Grand National tested with 245/60r15's all around, but some say 245's will scrub in the front on a full turn. The 235's won't. The 235's are also about 26" tall, about the same height as the factory GN tires (215/65r15)
Yes; took about 3/4 of the frame width out and re-welded the outer portion of the frame to the remaining inner part. Gained about 2" of room, just slightly further in than the inner part of the fender tub. I also welded a 1.5" mild steel bar at the top of the kick up for added support and I have a roll bar tied in on top of the spring cups. Picture shows the frame after before I remounted the body. If you want 255's or 235's, Gary's correct, you don't need to do anything with the 4" backspace wheels.
I think I might go with coilover conversion and and run some 3x2 on the inside of the existing frame then cut it out.