Thanks to all who have responded. I did do a search, but could not find the specific answers I was looking for.
Frank50 - good advice, but no I do not have access to another 1/2 ton to measure. I may just wait until I round up a bed so I can be sure to get the rear centered how I want it.
I repsect the purist who want to restore everything factory original like Denny, but I am more into making it the way I want it (and can afford).