AV7 can be fast but has limitations
only a few kits exist for them, parmakit, malossi and airsal, plus an old bi turbo stock bore.
the AV10 is still made and you can get killer parts for them, I have one that is scary fast. I also have a completely stock one. As for kits, you can get water cooled 47mm, 40mm, and some really insane air cooled kits from malossi, polini, bidalot, parmakit, athena, airsal, plus great cranks and big polini cases and the mykitteck big cases.. AV7=50-55mph AV10 start at 40 and go to over 80mph