MEM,
I've thrown everything at my bike and it was making a legit 76.2bhp on MCE Racing's dyno. I mean everything..... +2mm overbore (268cc), custom heads with inserts, PJ38 carbs, porting, stuffing, on and on...... And I was replacing the single ring pistons every 10-12 hours of run time. Obviously Master Patterson should chime in but if you want a real 70bhp, you're going to need to pay to play.
With my stock MC28SP engine and all the HRC goodies I could get my hands on, it made 62.3bhp.
Scott