Thanks again Donny,
I ran through all of that stuff in my head over the weekend. Routing the cable like I have drawn is totall do-able and will maintain the function of the shifter and trans without any fancy fabrication work.
When I got home tonight I ran the short cable I got with the shifter along my "path".
Up on top, the cable naturally falls down thru the pass-thru.


Underneath it sweeps right back toward the rear of the van. Mind you this is all natural, there are no forced bends in the routing.

This routing will work perfectly and it tucks the cable right alongside the old frame rail, well away from the headers and exhaust heat.