I'll tell you how my car is underneath, and you can look at yours to compare.
With the g-body frame, the lower control arm is only 1 1/2" away from the inside of the frame rail, so you can't really move the frame over as it would hit the lower control arm. With my car, moving the inner wheel well in, did not gain me hardly any tire clearance until I notched the frame. With the way a factory wheel well is curved, a flatter wheel well might gain you some room in front and behind the tire. I left the outer wheel well untouched and actually left 3/4" of the old inner wheel well as a surface to lap weld the new tub to.
To notch the frame, I made a vertical cut in front & behind the tire in the outer skin of the rail leaving enough distance for either a taller tire someday, or tire growth. Then I cut the top and bottom edges of the frame rail exactly 1" from the outer skin. Once this piece was peeled away, I then made a template and tranfered that to .090" steel plate and welded it together...filling the small gaps at the front & rear with small filler pieces. The final product looks very clean once welded, ground, and painted. The frame strength has not been compromised IMO, but I added an additional tube crossmember just to be safe. This tube runs on the inside of the frame from side-to-side and is located between the coil spring and the upper shock mount.
Doing this mod on a bare frame should be very easy as long as your careful welding not to warp the frame.
79 Malibu, 414 ci BBC, 3550 lbs.
11.12 @ 122 mph, 1/4 mile
6.99 @ 103 mph, 1/8 mile (new best)
[This message has been edited by Todd Geisler (edited 07-05-2001).]