Makes sense - they pulled pretty much the entire front end and interior out to put the vnt motor/555 trans and the shelby seats/door panels etc., so it wouldn't be that much more to replace the entire harness at that point.

Based on the body tag actually stating Shelby CSX and listing plymouth hood, grill, 60/40 split seat, etc., it seems like the 89's were specifically produced on the manufacturing line for Shelby with custom parts. I wonder if they deleted anything as part of that build? Wiring harnesses maybe?