Not the same comparison that you have,but my car did pick up almost 2 tenths going from pocket ported 452's to OOTB Stealths.I'm sure it went faster because of the compression increase due to the chamber on the Stealth's being smaller.

But I agree that your friend should wait and get a set of Sidewinders,Trick Flows or Indy EZ's. Had I known any of the heads mentioned would have been coming out when I bought my Stealths(and the Stealth's are good for what I needed at the time)I would have waited.