Honestly I was a little worried about that as well. The frame turned out to be 3/4" off on each side and I was considering making a frame splice that would make up that difference. I decided to have the inserts made anyway and give it a try first. By sliding the inserts 1/2 the way inside the engine side frame first and tacking them, it brought the rear frame to within 1/8" on each side. I slid one side in some, then worked the other side in some, all by hand and without the use of a strap side to side, then attached 2 come-alongs, one per side, and started ratcheting. I was pretty surprised when the 2 sides of the frame slid together with no real friction. The 12" insert is evenly spaced and the frame is still perfectly square. My only concern was the rear lower arms binding because of the frame being pulled in, but after measuring at the splice and at the control arm mount, the frame had pulled in only between the control arm mount and the transmission mount area. The engine side of the frame had spread apart almost an equal amount. Christo wanted me to cut the frame where the control arm mount is, but I'm lazy and didnt want to have to cut the mount off, shorten the frame, then reattach the mount. This was easy and I'm relatively certain that it will be plenty strong.