I think you're correct Luke and Tom. My car is a factory A/C car and there is a vacuum diaphragm powered vent under the cowl.
Definitely some weight that can be removed
Every ounce counts, I might even end up doing this to my chassis...
RIP - 1969 Camaro, green/black vinyl. BBC, th400, Holley EFI, 4.10 TrueTrac Dana 60, too much rust and not enough traction. 11.015 @ 111mph