The ring end gap is the least of your problems. I bet you have lots of cly taper and a large piston to cly wall clearance. If the motor should have been bored out and it wasn't, then you will have lots of clearance in those areas. I would not get file to fit rings because if you set it for the top and have lots of taper, you will be too tight at the bottom. The first tool an engine builder needs is a good set of mics and snap gauges( or dial bore gauge).You will use them for the rest of your life. If you have .005 or more taper, then put it together and save for some pistons and a bore job later. Mark