Faster gem

Hi I am the proud owner of a 2008 Gem I have installed Ride for Fun’s motor and charger and 150 ah batteries 22.5 wheels and tires. And can drive at 32 to34 MPH. While this is ok I am looking to hit 40 to 45 MPH.
I am looking at a gear ratio change but I am not sure what the ratio is on my stock 2008 (maybe 14to1 but not sure) and seeing 6to1 8to1 and 10to1 ratio’s out there just not sure which is the best way to go. From reading this forum it looks like call to Marlon might be the way to go. I have seen gear ratio changes when just the pinion gear is changed to make a ratio change. But it looks like all the gears are sold as sets. Is the ring gear bolted or riveted on? One last question is a controller reprogram required for this and should I try that before the gear work? Any suggestion?