Rewelding the ends on a new aftermarket cylinder shouldn't need much precision, unless I'm not picturing this right. If you have a portaband you can cut the ends off and take it to a welding shop, they should be able to get it close enough by squaring up the old end with the new cylinder tube. Are you by any chance in East Aurora Illinois? If you are, I can tell you where to take that to have it welded.