That could work... interesting to note that the dentside version of these F5-800 truck cabs still used the 68-72 dash for the better instrumentation, proving the cabs share internal architecture.
Some discussion on the why of desiring an accurate cab...
All for the want of taking a tooling mockup out into the sunlight with calipers, measuring tape and a calculator...
I'm guessing that the GM guys are hoping the licensors care a little more about representation of their intellectual properties than the Ford
reps apparently did