I noticed something the other day on a photo someone showed me. The dust trail on the 70 RR has an X on the bottom as well as the bird portion. That must be how it was supposed to go on. I see some at shows with X on top and some on bottom. Then it made me look at cars without the dust trail and just the bird. The one without the dust trail looks like the 1969 door decal as the 1970 has the dust trail starting at the bird. Was the 1970 bird (no dust trail) the same as the 1969 door one? Am I correct in saying there were two different bird decals for 1970 depending if the dust trail was ordered or not?

Here's a copy of the part number list (and placement) I saved years ago for all the 70 decals.

It is my understanding on the cars with the full 70 dust trail stripe, that the little "x" is supposed to be facing down. Although it is not clearly indicated on the factory instructions. I could see how it would be easy to flip over and no one would ever notice unless you are specifically looking for it. Most of the cars I look at have been repainted and/or stripes added. And I have seen them both ways--even on different parts of the same car. My car had all the "x"s on the bottom except the passenger side front fender, where they were on top. My guess if it is so easy to mess up on a repaint, the guys on the assembly line back in the day probably messed it up sometimes, too. I don't have any factory original paint dust stripe cars around here to check my theory. But my guess is the guys on the assembly line weren't being that picky.

That said, the first section of the stripe attached to the road runner's feet has the "x" on the bottom (as you said) so logic would tell you the rest of the stripe should go on the same way.

On all the full 70 dust trail decal kits I have seen--the background is gold, and the section of dust attached to the road runner's feet is cut off square like it was cut with a scissors. It cannot be used as-is by itself. (Decal #1 above)

All the "no stripe" 70 cars I see, the background of the dust is black (not gold) similar to the 69 decal and the section of dust trail is rounded, not cut off square. (Decal #9 above).

Again, I'm no expert and my car was a repaint, so I'm sure someone more knowledgeable than me will pipe up.

The "X" in the stripe is supposed to represent a footprint so they are supposed to be on the bottom.

there is a black & white 1970 Road Runner press photo - close up of driver's fender with dust trail strip - It's "up-side-down"

the stripe isn't supposed to be a straight line - here is the layout per the above instructions it starts in the center of the 1/4 scoop then moves up & over the wheel well opening