I'd forgotten about the mid-rear engine.
Fixed wheelbase; driver moved to the rear, front seat is a semi-reclining rumble seat with the seat cushion between the Mustang A-arms where a front engine would be. In race mode the passenger seat becomes crumple zone.
...otherwise, Here's an example of a variable wheelbase truck. One of the two driveshafts is
added:
http://justacarguy.blogspot.com/2014/06/international-harvester-sightliner.html
And the Rinspeed Presto from 2002. The chassis must be thicker by at least the distance between the chrome bars (either that or tiny people):
________
So, you're going to unbolt the front and back half and slip a spacer in between?