Michael, I’ve been karting for 13 years, and what I try to do is beat my best at that particular track in that configuration each time I go to that track. Sometimes it might be years before you best your time. Recently I best my time at this one track by 1/2 of a second, a time that stood for 3 years prior.
Since you are a big guy, I really don’t know what motor package would be best, you did however pick out the right frame size. Have you driven anyone else kart? That might help you decide on the motor package.
Welcome to the sport of kart racing, it never gets dull, always looking for that extra that makes you faster.