You can run either Scott as you say. Theory says the divided will spool faster but I've not seen an identical back to back test prove that yet, there have always been other changes that muddy the waters.
If you really want fast spool then you need to step away from the tubular manifold. However if youwant 700hp+ with "as good as you're gonna get" in terms of spool with the stock rev limit then you should probably go for an undivided manifold with a quick spool valve from SP and a divided turbo housing. Next best after that would be one of Mr Whiffins fully divided setups.
Precision turbos are not designed from the outset to be used with divided housings. Apparently the design of their turbines (in general) is relatively insensitive to divided vs undivided. A BW turbo on the otherhand will generally perform better with divided - or as it was put to me.....perform worse with an undivided housing compared to divided. There were a few threads on SF discussing this in detail but I can't find a link now.
I bought two housings for my turbo with a view to experimenting to find which one worked best. IMO, doing it any other way is a bit off the ideal as no two setups are truly identical so you're always going off the back of someone else's opinion and similar(?) setup.
To give that some context - My 0.81 undivided housing on the T67 (allegedly relatively slow spooling) spools faster than anything else I have seen at SRR except for Wez's little PHR61mm tubby. The wall of torque I get is phenomenal.... 590lb.ft @ approx 4600rpm (with over 500lb.ft from 4200-6200rpm) is not to be sniffed at. Most 67mm tubbys are down on that. I'm not looking for an out and out comparison here but I am saying you really need to pick the whole package to work together or you'll lose out. Cams, headwork, turbo design and A/R all link together and you need to get it right to reap the benefits of each component as a whole. I spent ages pondering mine and bought and sold two sets of cams and two turbos plus a full PHR tubular stage one kit before I ended up with what I have now.
Are there any items that are 100% fixed in your spec? You need to nail something down and then start matching the rest of the spec to suit IMO.
The 6765 will have to use a ported compressor intake and if you are using stock cams you may still see a little surge if you go for a 0.81 exhaust housing. If you are using (pretty much) any aftermarket cams then the 0.81 should be fine as it won't shift enough air low down to run into surge issues. The 6765 seems to spool fast anyway so I wouldn't get too hung up over slow spooling...but that depends how you drive too. There seems to be an even split on SF of people running the 0.81 and 0.96 - both undivided.
Hope this helps mate, sorry if I added more questions than answers!