I think it is. Pretty much all I have ever ridden in the past 15 years is MCX. Except one year I had a propane Nytro built by Brad Story. Still love the pump fuel reliability of the MCX product.
I think most big name setups are reputable. Some kits to look into are mcx (the kit in question), hurricane performance, One Stop Performance, and evolution powersports. I recommend getting an air to water intercooler setup; they are way more efficient and consistent than an air to air setup. Stay away from MPI; their kit does not provide you with ability to upgrade for big power later on.
That is a fair question regarding gearing and clutching. But, in my experience, dave knows how to build reliable race engines. He has experience helping customers with basic turbo kits, building 600 hp turbo race motors, which are transplanted into mountain chassis for chute climbing, and testing the limitations and tuning parameters for safe operation on the dyno and in the field. To his credit, a lot of big name racers work with him to build record setting sleds. If someone wanted to know more, he or she could call him.
Personally, I recommend calling as many companies as possible and picking the one that provides a good product with the best service.