I'm not 100% sure... are you're wanting to install another tachometer - one that can read back to you the max RPM you achieved? Why??? Just wondering... what purpose?
I'd probably just point a GoPro at the stock tach and then watch the video.
Is this the kind of thing you're looking for? http://magsarus.com/tachparts.htm
1991 Suz VX800(project), 1986 Suz Savage (daughter's bike), 2001 Ducati 748, 2007 Honda VFR800, 2015 Kawasaki ZX14R, 1987 Buick Grand National, 2013 Subaru BRZ