Thanks for link, we live in Dunedin New Zealand, we are 120 miles north of Burt Munro's home town :-)
Attached is the result from the flow bench testing, number 2 was the original head from the 650 Super Rocket which had be lightly modified, mainly just around the seats. One of the other heads was one of those "special performance twin carb heads" offered to American owners.
Hope that helps.
If you work out how much air a 650 motor can pump, they all can handle it no problem.