To bounce off what Andy stated, MOST bracket engines will not be capable of making anywhere near 20" of vacuum, many pumps out there also will not build 20"
either, especially with a wet sump oiling system. FWIW we run a Moroso 3 vane on the dragster and make 14-15" my car is an enhanced 4 vane and can see 19-20", we run both unregulated, both were built to run a vacuum pump. The heads up car we can get 22" with a wet sump, that's a very high number on a wet sump. Most bracket engines will be 8-10". Is there power there, that is debatable but you will eliminate any pesky oil leaks for sure.