I mount the cab first and then make the frontend fit to it.
I just went out and checked on my squattie truck and roughly from the door front edge to the centerline of the tire is about 29 1/2"
I would start there with setting the cab on blocks on top of the frame, (If I remeber right you will need to keep the back of the cab around 3" above the frame)
I would block the body in to place and then when its secure I would fit the frontend to check to make sure that the tire is centered in the wheelwell and when I was happy with how everything fit I would make the cab mounts and then make the frontend mounts. Ron.....

make sure you take pictures and post them as you go