Theres a lot of talk about those turbine housings being junk. I'm not convinced that they are a viable option yet. Definitely do some more research. Also, the to4b housng fitting better isnt necessarily a good thing, it only fits betterbecause it is smaller. You can get either housing from any turbo vendor, but you rarely hear about the Bs because most vendors dont list them on thier site, very few poeple want them. Back in the days of hte mutt turbos though, the B was standard, and the E was an upgrade to it.
I personally would even bother with a hybrid turbo. For a 50 trim type perfrmance I think the 6H 20g is a much better matched setup and flow is only 2 lbs less at 48. Even better if you get it with the 3" inlet housing like the one used on the red/green. Bigger housings mean more flow with less boost.
Spool was 3700 rpm to 25 psi IIRC. In my opinion the best bang for hte buck street turbo out there this side of a EVO16g. When going with larger than 50 trim turbos, I still woudlnt bother with hybrids, but rather go to a full garett and enjoy all of its benefits. The only trouble is that you pretty much have to go with a tubular manifold, but the new braced SFPs just dont seem to be cracking anyway. But now I'm getting ahead of myself. If you do go with a hybid I would consider going with a SBR manifold to space the turbo out so you can run the E housing. Not worth half asing it and regretting it latter. Do it once, do it right
Also, a bad turbo seal wont bypass enough oil to lower presure noticeably in my experience. Pretty much have to watch the level.