Engine Cooling – Was the engine rebuilt? Is it the original 260 bored out to what size? One cause of over heating is caused by overboring a 260. Ford recommeded nothing over .030.
Speedometer – probably needs a rebuild if fluctuating. If it reads too high or low I would suspect wrong tire size for the speedo gear in the trans or maybe the rear end ratio is throwing it off. The original ratio of 2.88 is good for highway cruising.
Front end – Could be tires out of round from sitting. Check the date on the tires and see how old they are. Are the bushings original? You may need to replace them.