The pickup is a Dimarzio Model G and yes it will fit under a '76 Tbird cover from greatdealz. This one is not covered. Here is a picture of it, note the butt ugly creme color, I can live with it cause they sound so good.
There is a model G installed in the neck position of my 2001 Gibson Tbird (The Butcher Bird) no potting or messy installation work the Model G is screwed in to the cavity floor and the the cover right over it. The height is not adjustable but things lined up real good no need for adjustment though I could put a little foam underneath to give it some.