Some companies make special covers to match up with their gear drives such as Edlebrock while most drives are used with either stock or other aftermarket timing covers... It may be possible to use a cam button depending on which manufacturer's gear drive set-up and which timing cover you are using... You might want to check with the manufacturer of the drive to find out what recommendations they have...

Also another note, many gear drives are not recommended for high-winding engines I have seen some that are not intended for use over 7000 RPM...

Hope this helps some...

Dave Brisco