why did you tear down the motor in the firstplace???
i would get it honed/or bored and then put in a new piston and rings but thats just me..... but first...
i would take it to your local machine shop and have him look at it first... it would be real costly to take a chance and put it all back together and then have something go really wrong with it!!!
its happend to me ....slow down,take your time, and you should have a more harmonious outcome....