I called Bill Bune Enterprises and asked about getting my 78 DT400 cylinder checked and freshened up. I got Josh and he was very friendly and ready to help. So I sent my cylinder and current piston (second overbore). I also sent a third and fourth over-sized Yamaha piston and rings so he could check out the cylinder and do whatever it needed. He received it Friday and called me today (Monday) to say it was done and ready to come back to me Tuesday! Next day service....what?....that's how you build a loyal following. The cost was $99 shipped back to me. He went from the current second overbore up one notch to the third over bore and verified correct ring end gap. With including the new piston and rings and Josh volunteering the clearance info I'm confident of a plug-n-play top end. It will get a total cleaning, as others here have reccomended, before assembly.  Can't wait to get the parts back! I'll use Bill Bune again!