45-50 is a good cruising speed for 216 equipped with 4.11 gears. And 50 always seemed too fast for my truck.
As for maximum speed attainable, somebody will probably post that their truck will do 120 mph uphill with a 1,000 pounds of cargo, but the 1949 truck salesmans data book has some math formulas that puts the theoretical top speed well under 100.
