I have found 99/121/74 to work great with massive power and a wide power band.
I have tried them with the intake down further at 79 or 80 and they are more violent and peaky.
I usually slightly widen the exhaust and flatten the roof a bit to take advantage of the raised uppers, widen the transfer tunnel towards the exhaust port some and open the uppers flat.
A red97 port on the flywheel side with a 3/4" hole under it and the factory outlet elongated all the way along
They tow like a freight chain at 12500 RPM running an unlimited coil