That kit is not necessary IMO.
You just need the ring and pinion, shims, possibly a rebuild kit depending on the condition of your rear end as it sits now, some full synthetic lube (I would prefer 75w140 over 75w90 personally,) and a speedcal from Brothers or Dallas Mustang to fix your speedo.
It'll cost you like 130ish for the gears, 20 something for the lube, 90 for the speedcal, and 80 for the rebuild kit. That's barely 300 bucks.
Check out
http://www.brenspeed.com/mustang_46/rearend.html at the bottom for the rebuild kit info. MT might have rebuild kits too.
I got FRPP gears in mine, I'd stick with Ford over Motive.. but that's just me.
