In the following post there is a good picture comparing the hub supplied in the kit with the Hoosier one. My understanding is that the one the kit is better than the OEM one. The primary reason that I did the upgrade was to get an OEM-like tone ring for traction control. So you have three known options; free

, $1,175 (when you include the adapters) or $1,400 (plus machining). The Hoosier's are heavier duty, re-buildable and come ready for press in or threaded studs, but they're more expensive and require the uprights to machined in you have a newer car.
Ken, if you recall my uprights had a lip on the uprights that I had to machine off. Your earlier version didn't have those lips so I'm wondering what happens with someone with a newer car copies your upgrade... will they will need to machine them off. Looking at the pictures, it doesn't look like it, but it would be great if you could check how they compare in that dimension.
http://www.gt40s.com/forum/502086-post104.html