pwake7,
I have JRC 3000 4kw radar mounted in the overhead E box in my 1993 230. It is a CRT screen and 24 in. dome. The setup works well but I have an aftermarket hardtop and E box. The box is a little larger than the factory box. The hardtop is almost exactly like factory except about 3 - 4 in. taller. The electronics are 2003 vintage.
I have a Garmin 2006c and RM ST 5001 AP mounted in the lower E box door. I had a new door fabricated for mounting the GPS and AP and had to move the latch over a few inches due to the size of the GPS. That way I can still use the box for storing items. My arrangement works well for me. Have fun with your Gulfstream.