The topmost pipe is larger than the rest of the rack. That one measures at 3.5" outside diameter.
The rest of the pipe measures approximately 2.875" outside diameter.
2.5" and 3" SCH 40 pipe should match the outside diameters perfectly.
I know it's not how your diagram is set up but I measured most dimensions from center to center. Exceptions are noted.
The topmost 3.5" diameter pipe is exactly 72" wide.
The vertical posts are 53" center to center (side to side), and 17" center to center (front to back of truck)
From the top of the angle iron foot where the vertical bars are welded to the bottom of the 3.5" tube is 56.75"
From the top of the angle iron foot where the vertical bars are welded, the center of the first horizontal bar for the basket is at 24.5"
The next bar up from that is 13" higher, measured center to center.
If you measure just the vertical height difference, the next bar is 10" above that, measured center to center. This bar is forward approximately 1", as it's on the curve.
The last bar (with the center brace tube) is basically centered horizontally between the center of the 3.5" top tube, and the center of the 2.875" tube on the corner of the curve. It's approximately 8" horizontally from the 3.5" top tube, and 8" horizontally from the tube on the corner of the curve.
Sorry if it's a bit confusing, I haven't had time to draw a diagram or put the measurements on a picture. I had one drawn out many years ago but have since lost it.
