I was following this question on the 70 RR dust stripe thread. That drawing also referenced a zero line (vertical) and an implied horizontal zero line.

I went home and tried to determine where the “zero inch line” (on that drawing from the other thread) would be for the vertical and horizontal measurements based on my 70RR with just a fender bird (not sure if original). Here’s what I got (and I don’t like it)…

Vertical zero is NOT the pinch weld, style line, door edge, wheel centers, or obvious frame points. As near as I can tell, it’s at the left side Chrysler symbol. I based this on laying down a masking tape “dust stripe” and measuring stuff and looking for landmarks approx 13.27” down. There is nothing else obvious on the side of the car. On a frame drawing from the service manual, “0” is measured as wheel center line. Not the same zero.

Horizontally I come up with zero being the front edge of the cowl! This is pretty close to having the fake scoop edge at +75” and puts the beak of the bird at -45” (per that factory blueprint). I wish it was again the pentagon but it’s not.

The bird on my car is NOT beaked at -45” but again I don’t think it is original or didn’t matter as there was no dust stripe.

The frame drawing shows some gauge holes on frame cross members but nothing really aligns with the +75” scoop placement.

I don’t like my answer. Having two different elements for zero lines makes no sense.