23/25 and 24/24 are almost exactly the same, 3.27:1 for 24/24, 3.28:1 for 23/25. Assuming a present engine sprocket of 23T and tranny is 22, your present ratio is 3.72:1. If you've a 24T engine, it's 3.57:1. You're really going to have to change the countershaft sprocket to get it geared up to a nice cruising RPM range.
Just my .02 worth.