Our three-year-old '69 225 /6, loaded with 1,200 lbs of stuff in the trunk, back seat and roof rack for a cross-country move, went across Texas from the western panhandle to New Orleans, a little over 1,000 miles, in almost exactly 10 hours, including stops. The usual driving speed was between 105 and 110 mph (with a one-time max of 117 mph) in temps over 100-deg. F. That August heat was our major incentive to get across Texas quickly! A couple of years later I had to replace the back wheel bearings. We had no other mechanical problems.