I believe in keeping it scale. So with that in mind a 300" wheelbase at 1:14 scale would be about a 21.5" wheelbase. That is measuring from the center of the front axle to the center of the first rear axle.
Speaking from experience driving a 300" WB tractor on the street is not easy. There may be longer ones out there on the but I've never seen one.
But in due return I have a 300" WB Wedico pulling a 53' trailer and it handles very well.
