gear install question

hey guys - im gonna go with a set of FRPP 3.73's in my mustang to replace the stock 3.27's. i got a $300 gift card to summit for my birthday, and i just wanted to ask about the install kits. they have a couple options.

http://store.summitracing.com/partdetail.asp?part=RAT-3008K

http://store.summitracing.com/partdetail.asp?part=RAT-3021K

http://store.summitracing.com/partdetail.asp?part=RAT-305K


i was leaning towards the last one (also the cheapest) mostly because, i dont think at 42k i would need to change the axle bearings/seals. it still comes with carrier & pinion shims, bearings, seals, everything except the wheel bearings/seals. and for $30 less, i think i can deal with not replacing EVERYTHING in the whole axle. am i wrong here? or is there no harm in leaving those as-is?

i would get one of the girdle covers, but i dont NEED it, but i DO need an SFI 3.2A/1 fire jacket for englishtown, and im trying to stay as close to $300 as i can.

well, the bearings and seals are on the outside, correct? if they ever do go, i can always get a set of federal mogul's or ford OEM's at 20% off list through my job. i've got no problems with them now. i guess ill see what happens with the originals.