you will have to add links
im running a 6/62 thick pitch setup & the 62 tooth thick pitch rear is almost the size of the rim so keep that in mind
62 thick is similer in size to a 74 tooth thin sprocket
i used a aussie thick pitch flame cut sprocket from billet racecraft
they use them on the R1 bikes with reduction gearbox (ctv) but had to have the center shimmed & bolt holes re drilled to suit a cag rim
here is the 62 tooth thick slightly larger than the 72 thin but has good pickup & a decent top speed
& this is a 74 thin 
for best value you could get a set of 6 rear sprockets from ozminimoto for $35 plus $7 for a 6 or 7 tooth front pinion
Ozminimoto - Mini Pocket Bikes - Product Detail & some new chain + joiner links so you have plenty of options to go with
