It seems the exterior styling evolved from the P2, 3, and 4, the interior not so much.
If someone does not beat me too it I will look up a P2 gauge cluster photo or video in the morning as it is actually very different from the P3 and P4 style and there is actually a visible natural evolution in the dashes between the P2 and P3 and then again between the P3 and P4.
While both the P3 and P4 have shared recycled Geo Metro gauge clusters these are merely stand ins for the Elgin design, which I believe was already on the drawing board, The overall dash has actually evolved considerably between these two models for such a small dash. In the P3 all the items on the dash protrude individually from the curving dash and all the lines are curved and blended however on the P4 everything is contained inside that central hump and the curves and blending have given way to flatter surfaces and squared off corners.
With a little more comparison using the photos I have from this weekend I am now nearly certain that the Elgin prototype I got my hands on this weekend is the very same one we saw in Tech Talk v5 back in March however we all thought that was a rendering when in fact it was a physical prototype. My guess is that may have actually been intended to be the P4 dash as we also know they are the same size as Jerome told me that however for whatever reason it never made it into the P4.