I'm in the search of a decent SST 120 powerhead and have found a couple now that I'm looking into (one of them is supposedly a XR2)...

I know that some powerheads here in Norway are mixed parts from XR2 and SST 120 and have heard that it is mainly the flywheel, ignition (?) and starter that is the real difference from the leftie SST120 and XR2 but how can I tell?

Is the serial# also the same?

Thanks,
Lars