an a5 head on an a3? now u got my attention! will it really just bolt right on and fit properly? if so, im gettin one! their only like $25 used from the moped junkyard, and my A3 has overheated on hot days b4, but that was also cuz i was running a little lean, got a bigger carb jet, so i'll let you know if it does do it again (yes i will run it wide open for miles on a hot day) also, on the subject of this post, im pretty sure all the new Tomos' have 22 tooth rear sprockets, A3SP's have them too, all other A3 models were 24 tooth, only really modifiable gear ratio change is the front sprocket, 25=more low end 26=stock 27=more top speed. ive kept my sprocket stock, because we have large hills here in Mass, but also "hairy" 50mph main roads, so i wanted a good balance of both top and low, i may still go with the 27tooth tho.