You can fit a pretty tall driver on a standard kart chassis; a lot of it is seat positioning.
I agree that building a kart is a lot of fun. Depending on your ambition and skill, you can do quite a bit with just about any race-spec chassis.
To give you an idea, I built a CR-80 powered shifter out of a Coyote Widetrack chassis, complete with updated bodywork and parts straight from factory-spec shifter karts (Coyote doesn’t offer anything for shifter karts). And the entire kart can be returned to a clone-powered setup in one afternoon; there’s not one weld or permanent mod done to the chassis, everything bolts on.
The point I’m trying to make is that it’s important to have a good foundation, regardless of what you’re trying to do. It’s challenging, but extremely rewarding to build something one-off.
Good luck, building (to me) is almost as fun as riding.