Bo,
You are, of course, running under the FIM rules which are slightly different from the AMA rules. FIM has no "pushrod" class as such, so a single cylinder 500cc can be overhead cam, 4 valve, etcetera, maybe even 2-stroke. I did a quick read of the rules and that was my interpretation. Running an old pushrod motor under these rules seems a little tough, although I can't find all the current records. Interestingly, the version you gave me said that Tad Meadows has the 500cc non-streamlined record at 108 mph on an old Gold Star (I think). I am, however, building my bike by the SCTA current rules, which allows more streamlining at the back than the AMA rules, but rumor has it that that will change for 2012. The current AMA rules allow the following: "With the rider in the racing position, the rider must be able to be seen (hands and arms excluded) entirely from either side." I interpret this to mean my hands and forearms can be fully faired.
Thanks for the info.
Tom