Re: Wiring differences from 1966 to 1967 Skylark...
When I installed a 455 in my '64 I ordered a replacement engine harness for a '64 300 and it worked just fine with some minor adjustments. Rather than convert a '67 400 harness I'd order an engine harness for a '66 300 and work with that. All other wiring harnesses should be for a '66 too. A '66 GS400 used a Nailhead engine so you'd probably end up making more adjustments that you would with a '66 300 harness, since the distributor is in the rear of that engine and the starter is on the driver side.
64 Skylark Convertible
462 w/ Stage 2 heads, TA 212 cam, B4B intake
3.73 12 Bolt w/ TruTrac and Moser axles