Originally the measurement is 24 in. between the middle and rear mount, like mentioned above, you need to stretch the frame 13 inches, and when done you should have 37 in. center to center between the mount's, I used 2x6 1/4 wall rectangular tubing to stretch mine, and I overlaped the joint's by about 6 inches on both sides, it work's like fish a plate to strengthen the frame, and then also like mentioned above, you move the middle cab mount's out 1/2 an inch on each side. This is really not that difficult at all.Good luck with your project.