Background: My lathe is a Craftsman/Atlas 618 (sleeve bearings) probably made in the '40s. It had been sitting for 15 to 30 years before it was given to me as mostly a pile of dust and rust. I took it apart, cleaned it, removed the rust, slapped on some primer, and with the help of the 618 Yahoo group was able to replace most broken or missing parts. The result is a mostly running (if well worn) lathe. The issue is this. The headstock is lower than the tailstock. A center placed in the tailstock points above a center in the headstock. My choices are to mill the tailstock or shim the headstock. I've not the equipment or experience to hold the tailstock square and level for milling. With shims I can safely make mistakes. I want to measure the difference in heights to figure out what size shims I need. I was thinking of mounting some drill rod in the four jaw and adjusting until it runs true then measure the height with a test indicator in the tool post. Next I'd put the same drill rod in the tail stock. Measure again. Calculate the difference. That should be the thickness of the needed shim. Will that work? Is there an easier way?