I'm running mid 12's on a RADIX'ed 5.3 ... stock pulley too. It's only seeing about 7psi.

If I was going to do something else major i'd stick a 6.0 under the RADIX and up the boost a little more. 11's for sure.

There's nothing like instant boost! While your waiting on your boost to come on at 3k rpms, I'll be pullin on ya hard.

I say go with the RADIX. It is the most complete supercharger kit too. VERY nice and well put together.