First off, the Mav/Comets have timing chain and gears, which does the same job as a timing belt. Replacing one is quite complicated if you are a novice. My advice is to find an old Chiltons or like type repair manual and study that section. I am not sure if there is a scheduled mileage replacement on timing chains. I have always considered 100,000 miles to be maximum on them and I usually replace items like that at the 50,000 mile mark.
At 54,700 miles you probabily dont need to even worry about your timing chain, they usually last 100,000 or more. With most V8's the timing chain last as long as the rest of the motor. Replace the cam chain and gears when you rebuild the motor or swap in a new cam. Is there any reason you think you need a new cam chain? or is it just because of the miles on the car?
Its a 302... Yes, the miles concerned me. I’ve flushed the radiator, transmission, brakes, and slowly doing the oil. The motor doesn’t burn oil, but it does leak, same with the transmission and the radiator. Is there a good oil additive that I can run in the motor to wash out some of the deposits? I was going to remove the valve covers and clean those really good.
