What are you refereeing too when you say:
"I've still got to change the vertical firewall harness connector to horizontal so it will clear the AC box."
Poor choice of words! I should have said the wiring harness bulkhead connector needs to be horizontal rather than vertical so as to clear the AC unit.
I've attached a picture of my Dart's firewall with the vertical opening (haven't done anything to it yet) and another of the donor showing part of the horizontal opening. Also need to mention when converting to AC, you need to use the 65/66 V8 (and slant 6 with factory AC) gas pedal and cable assembly. The rotating rod (for the slant) just won't work.
Also took the measurements you asked about:
A - 3/4in
B - 6 inches
C - 7 inches
D - 5 & 1/8 inch
E - 4 & 5/8 inch
F - 3/4 inch
G - 3/4 inch
You didn't ask for them but the large hole for the upper AC line measures 1 & 1/2 inches while the smaller is 1 & 1/8 inches,
Looking at the difference between the 65/66 firewall and later, it appears that when converting to AC on the early A's one will need to use the 65/66 under dash components. Any other questions, ask and I'll try to answer them.
