Start with getting longer brake hose and throttle cable. Your bars are going to have to come way up, 8-12 inches. I tried to do the exact same thing with a kx100 but only got as far as the Hi atv bars, which stretched the cables to the limit and weren't nearly tall enough to accommodate standing.
The motor was pretty cool but will need a flywheel weight, it chugged ok. .
I abandoned my project because it wasn't quite suitable for the woods I ride in. The short wheelbase makes it feel deflection-prone. The 16 inch rear spins up pretty easily. I didn't get around to messing with the suspension as I 'm lighter than you but i think that will be a critical element.
I sold mine for $750, you might want to try a used one before getting a shiny one but i'd love to see somebody go the whole way on a kx100/ ktm105 project.
I'll try to find helmetcam footage off of mine.