I would also have to recommend the P5. There arent many significant differences between the Nova based P5 motors, but a few companies use different carburetor parts and different sleeves. The JP B5-N is a great 5 port motor to start with, if you have the money for it.
I would recommend the P5 over anything though, just because it has the best overall powerband. You can use the Jammin JP-2 pipe on the larger track to get all the top end out, and then I would DEFINATELY recommend the Jammin JP-1 on a smaller indoor track. I race at a small indoor track (www.charlotterccenter.com
) and all the fast guys are running thr JP-1's.