I think the wheel base on all the superkarts are close to the same,it’s more about seat and pedal placement . It shouldn’t be to difficult to extend the porch if needed. There our a couple guys out west here that are over 6′ and don’t think they have done anything special.
Justin – Russell Anderson used to make two different model chassis – one was a Maverick and the other one was a Mirage. The Mirage was made specifically for the 250 twin cylinder class and that had a long wheel base – I am pretty sure that had a 46″ wheel base. That kart is no longer manufactured; the Zip Eagle II had the same wheel base too.
You can still buy a Maverick from Anderson, they have a couple to choose from, they are referred to as a Division 1 or Division 2 Maverick. Depends on your motor package you want to use. Here is a link to his site: http://www.andersonkarts.com/ – neither of the current Mavericks have a 46″ wheel base, they now have a 44″ wheel base. I am 6′ tall and fit in my Maverick no problem!