I assume you're asking about the maximum RPM (redline)? According to my factory tach, mine redlines around 4500, but in the 5 years I've owned it, it has never been over 3000 (and it's only seen that a couple of times). With the age of mine (and it's not nearly as old as yours), I'm afraid that thing may fly apart <img border="0" title="" alt="[Eek!]" src="eek.gif" /> ! Generally speaking, I don't see much effect after I get it above about 2500 rpm, so that's when I usually shift.
Currently an '86 CJ-7 and a '77 CJ-7 Golden Eagle---#4 and 5 following a '01 Sahara, '90 Sahara, and '85 CJ-7....