if you rebuild your engine then that means that your going to be using the existing engine block, so in essence, no you cant start it from zero because you will still have that many miles on the original block. Now if you were to just build your own engine and everything is brand new, block, pistons, ect. , then you could turn your odometer back to zero if you like. Although you still have that many miles on the frame itself, and if thats all ok ( no wrecks ) then you should be good.