please use the search function or the wiki this topic has been beat to death.
basically the av7 is piston ported and the usa motor for mobys there are very few cylinder kit options if any for this motor
the av10 is a case inducted reed valve motor that was not used on bikes in the usa but mounts in the same fasion as the usa av7 motors. it has a bit more power stock however th real value of it lies int he amount of after market support it has.
while there are no kits for the av7 there are 6 or 7 choices for the av10