I have seen some 914's that look "taller" than others. Not sure if it is the overall height of the car or the height of the window, or maybe the paint scheme and tire/wheel combos make a difference, but were cars of different heights produced over the years? Did window dimensions vary?

No. The dimentions were all the same other than the bumpers on the late cars. The nice thing is that almost everything, or at least many things, interchange through the years.

US cars where set a little higher than Euro cars to meet headlight standards. I do not know the details though. I want to say something like a 1/2" difference.

1/2" makes a difference to the DOT mugs.
DOT
(Don't Otherwise Think)
(Down On Teeners)
(Dimwitted Overrated Tweakers)

I could go on.....

But that was merely done with a tweak of the front torsion bar adjusters. The rear ride height was not changed. (Which would have required different springs or other hardware.)

--DD