rev limit on 3.73's...
 

My rev limits before the trans can change to the next gear.Do I need a shift kit or can the Predator do the job just by increasing shift firmness or shift points?Works fine with the 3.23.

You probably just need to correct the MPH shiftpoints,
this is what's lagging RPM when you change gear ratio
upward. The Predator gives you this access. Get out
your calculator, figure up the new MPH by scaling old
ones by (3.23/3.72) or 0.86x and see how that does.