Dunno about the different levels, I rebuild a spare c6 with a kit from Broader Performance and it had the SK6 kit with some extra stuff. Had instructions from Broader and Trans-Go.
either way, the whole system rocks. I accomplished two things with this method: build a mean trans that can stand up to more power than I can throw at it for about $600 total, and learned enough about the trans that when something does go wrong with it I understand what the problem could be.
Building a $1500 trans yourself = $600
The knowledge of fixing said trans without having to call anyone or mail the unit back to an apathetic company that already has your money = priceless