[Paul2x]

I think Drift freaq said it best.

if you not going to do many mod's and want a reliable set-up, the 15' motor is a good option...b/c they usually have the least amount of miles.

but most 15' guys that want to make big hp #'s switch to a 13' head anyway b/c it make much more top end power so... if you going to build it completely don't waste your time

just my .02