I'm doing the rabbit mtn TT this weekend. It's pretty flat for the first 8 miles or so and then it's like 7-8% for about a mile and then ends with a about 400 meters of 13%. So the big question is what is the best set up? I have full on TT bike with disc and all and clip on for the road bike that is pretty light and zipp 303s. Recommendations?

Your TT bike will do fine. The top riders will get to the end without using a 25 tooth cog, but if you're not elite, bring a 25. Your numbers are a bit off. The first 5k are flat, the next 6k average 3% and the last 0.5k are at 13%. Your TT set up will serve you well to the bottom of the hill at the end.

just make sure to keep some energy for the last segment of the hill. I saw a lot of guys popping there. One even got off and walked.