Alright so I got a couple of updates from PTE on this for anyone interested I suppose. The 55-66 series compressor housings are all the same compressor housing machined to fit the appropriate wheel. The guy on the Phone (John I believe was his name) instructed me that the "SP" housing (4" in machined anti surge 2.5" out) has an overall housing height of 8.5".
The "E" housing (3" in 2" out) has an overall housing height of 7.5".
The information of the covers being the same across the board is the key information for me as it is my confirmation that I can go ahead and run twin 62s in place of my old disco potatoes.
Twin turbo build fabrication/pics - Page 2 - MY350Z.COM Forums
This link is to some research I found that Sasha was doing that confirms the 5557 to be the same size as the GT2860RS. I think the guy with PTE was basically telling me 0 deg clocked position overall height of 7.5" which I was only concerned with the diameter of the cone.
Anyways for those of you looking for a little more affordable,(in most cases more efficient) directly bolt on, replacement for your Garrett turbos; Precision turbos are out there!