can an A-body tow?

I towed a tandem axle trailer with about 7k# on it from southern OK to NE with a D200 crew cab that was already loaded with a 4k# slide in camper and about 1000# of books, My truck had a 225 with around 300,000 miles on it and an automatic. My average mpg for the whole 600+ miles was 11 and I ran 65-70 mph. Yes it is a truck, but the 225 can handle the load if the vehicle is up to it.