Cool Head dome sizes??

[LT250RMan]

Can someone tell me the dome size i sould get for a LT250R Cool Head if i want to run

92 Octane (PREMIUM)-----?

or

110 Octane (Race Gas/Avgas)------?

[GPracer2500]

I believe the 22cc head is for pump gas, the 20cc head for race gas. I'm not for sure if you can run the 21cc head with pump gas or not (I think you can).

I'd prolly just call pro-designs and ask them.