ok willy, so first the diff breather is extended so that when i submerge my axle in deep mud/water it wont mix with the oil inside causing u to need to flush the axle... its more of a thing u do to prevent a potential problem. There are other/cheaper ways to do this but i like the look of mine and it wasnt that bad (~$15)
So i got my 9 wraps from a member on ih8mud.com but there are a few guys here once in a while that end up selling a set. The 9 wraps are great for added height but dont do too well under continuous stress loads. The reason i wanted these over the 891s is bc i gained about 2" of height but i rarely ever tow anything. Since u mentioned u towed a bass boat, ur prob better off just keeping the 891s since i know a few other guys who have 7 or 8 wraps and have said it sags worse then the height of the OMEs while under a heavy load.
Well hope this helps u out, and ur rig seems to be coming along nicely...