Need dimension-frame tips to rear lic. plate.

[71C10SWB]

Hey guys, I'm planning on building a hidden hitch to go behind the rear bumper on my '72 swb.
I don't have the rear bumper yet, but the beds off and it's a good time to go ahead and mount the hitch. I need to know the dimension from the tip of the frame rails to the license plate mount for the styled rear bumper (non-step).
I plan to build a plate with a tube to mount the rear plate when not towing.

Thanks