This one has a very M-66 look to her...

Oh, I didn't knew that ova. Nice!

Old Masamune Shirow work. If you have a chance to see the full thing, preferably subtitled, I recommend it. At the same time, I also recommend the manga "Black Magic", from which the Black Magic M-66 OVA was drawn from (though the OVA focuses on a tiny sub-set of things as opposed to the manga's far larger and much more mystically-oriented plot). I should add to this I recommend pretty much anything from early Masamune Shirow, as a lot of it was inspirational, design-wise. The more recent stuff focuses far more heavily upon CG and is a little less suitable.

As a separate art reference, if I may, I would make suggestions for any and all of the Intron Depot series of books by Shirow, followed also by anything from Ken-Ichi Sonoda. They both have a good, technical style.