The original vehicle was itself a 'scale model', in that the fantasy interior would not fit inside a large airport tow tractor.
If you want to build a replica you have to decide if 1:1 means large enough for the fantasy interior or 1:1 to the movie vehicle. The movie vehicle is too wide for road use, I would propose keeping the width of the vehicle below 100inches by placing the driver at the rear top of the vehicle and the forward control cabin occupied by a large doll (the doll could be animated to look like it was struggling with the controls).
The driver would then look through an aeroscreen about where the roof spotlight is located (keeping the spotlight would help camouflage the driver).
Find the largest wheels you can, build the vehicle on an existing or tubular steel chassis incorporating Oddmar's suggestions. The driver would be on top of the rear mounted engine so controls and wiring would be short. The biggest problem is animating the turret.
The finished vehicle could be driven on roads to an event.
i was lucky enough to pick up a set of blueprints a few years ago, they are in my garage somewhere.
i guess you have access to these already?