There are several internal trans gear sets available ranging from a 13/40 [torque] to a 16/36 [speed]. These can be found on most of the scooter sites.
http://www.scooterdomain.com/category_s/739.htm
Install is easy, a press is helpful but not necessary. Keep in mind scooters and buggys are two different worlds. what gives performance in a scooter might not work in the buggy due to the weight difference. You will do better gearing for torque internally and experiment with weights and external gearing for speed.