You should be able to run in Tag Masters as the rule is usually applied as 200# with driving gear including helmet.
As far as engines go, the two most popular choices are the Leopard and the Rotax. We could get into big arguments but the bulk of whats at the tracks are one of those two. There is good support for both and they both have their advantages and disavantages. We sell and race both engines in our factory karts so if you want to call, I can give you more detailed information.
303-781-7829