without locking hubs (i.e. with the factory drive flanges) your front axle and driveshaft would be turning all the time.
Seeing as one of the alleged benefits of part-time is that the aforementioned heavy parts *aren't* turning, I'm not sure what the benefit of doing it without them would be. Not to say it's not possible, just donno why you would.
AFAIK there is basically one kit available new any more, the MileMarker (somebody correct me if I'm wrong.) Hubs, you can buy the MileMarkers (okay), the Warn cheapos (okay) or the Warn Premiums (more metal, i.e. less plastic, nice.)
The kit does involve opening up the t-case; I inherited both of mine installed, so I've not had to do it. Someone will chime in with the scoop there.
Both my Blazers have part-time kits and still get miserable mileage, so don't go thinking you'll save on gas costs.
I find that the turning radius is decreased, though, with the hubs unlocked, so I'd say I'm saving wear and tear on the front diff and tires.
YMMV.
-- A