The wiring goes in above the fuse box and plugs into the fuse box, you are talking about moving the bulkhead grommet to the other end of the harness if you move the power feed wire to the center of the firewall.
I just got off the phone with the owner of the first documented ZL2 car, Van Nuys 12C never restored with tons of paper, power feed is in the std location at the fuse box.
The early 01B - 01C Yenko's (these are the first 50 COPO 9560's X66 conversions) I know about have harness piercings in the std locations, if I am not mistaken the 1st 2 ZL1's were between the 12C car and the Yenko's and they are std location as is the early Berger ZL1.
Need a Link to the discussion you are referencing on Yenko.
I didn't know of any additional DOCUMENTED early cowl induction cars, doesn't mean they don't exist.