I see one issue immediately. It has square-profile car tires. When turning it will be riding on the corner of the tread, right at the time when it needs traction the most. And those corners would wear out fast.

There are big heavy motorcycles now which means suitable tires are available. But at that size and weight they'd still last only a fraction of what people expect from a set of tires. In 1967 there was nothing similar. They would have needed to contract with a tire maker to provide purpose-built tires.