Yeah, the air cooled costs are pretty dear when it comes to digging into the motor. Ninemeister (in the UK) some amazing work with these motors too, they also perform turnkey conversions / builds. I've spoke to Colin there a few times, very good people.
http://www.youtube.com/watch?v=lI1PjgCV_c4&html5=1#t=67
Those Blokes certainly could use some track day etiquette.