I have driven a lot of tractors in my life, and still have one in the shed. Can't say as I've been behind the wheel of one I would want exceeding 30mph. That said, the neighbor had an IH M that they put a Dodge 318 in with no other modifications. The increase in rpm alone increased the top speed to over 40mph. Only the brain dead would try that with a narrow front, but that pretty well describes the inbred idiots.