Donovan,
I think your thinking too much...
I'm not sure if the 366s have smaller ports, but I would not be suprized to find it so. (The H/D 350s are "suposed" to have H/D flow-restricive ports and valves).
Even if he 366s do have smaller ports, why would you want to restrict the engine so much? To gain a slight amount of low RPM power (at WOT)?
For us, where we control idle/cruise speed with throttle input, the throttle-blades is the restriction, not the ports and valves.
To put it another way, If you want more power to crawl over an obstical, you simply applie more pedal.
Granted, higher low RPM port speeds will increase low-end torque - but thats only during WOT.