I believe you were looking at a tap drill chart, not a chart that gives clearance sizes. I am assuming you are NOT tapping the hole, just clearance drilling. If so I believe a #19 (.166") will probably work. An 11/64 (.172") drill will give you a bit of clearance. Going by memory I think a #8 bolt is about .164" dia.
A couple things to point out:
1: Bolts are normally a little bit smaller OD than their size designation.
2: Drill bits are not reamers, they do not drill exactly on size, always oversize in steels. The amount oversize depends on tons of variables such as whether you center drilled, the point angle, the accuracy of your drill chuck, rigidity of setup etc. Assuming you don't have a milling machine I'd prefer to do this in a drill press, possibly using the other part as a guide if the hole is good in it. If that is not possible, you may want to pilot drill it first, that will keep the second (on-size) drill from going oversize. If you have to do this with a hand drill, I would probably step drill also. People tend to drill tapered holes with hand drills, the second drill will tend to provide a straighter hole.
I have probably over simplified my reasoning/technique. But I do agree, you need 2 close fitting holes reasonably well lined up.
