This is kind of an old thread, but there is a Picco P0 that is fairly fast.  It is either an.052 or an .06 and doesn't fit in the actual combat class. They are fairly cheap as an RC car motor at about $40 now because the cranks break pretty easily.  I would guess if the revs are kept down they may last but could be wrong.  A bit of work may need to be done because of the heatsink head and carb, but it could be good to fool around with.(it is a hobby)  The Galbreath heads and conversion heads for the Norvels and Cox's are ok, but now there are Merlin heads for about $5 that work well as I understand. I haven't tried mine yet but his regular plugs seem fine for the couple of flights I have had.  I am trying to justify getting a Fora, maybe some day.