Re: ?Recommendations for HF 90cc Engine Kit
You have to contact a dealer. I don't know where you are, so can't help you with that.
AGK's gearbox is wider, and less expensive, but offers better performance. Easier to service and customize. It's also less of an eyesore, some would say.
The Q-matic is slightly narrower and more expensive, but is smoother. Some would say it's uglier, too, on account of it's huge gearbox cover.