Supposedly we are to replace radial tires after 6 years. I generally might go 8 on a classic car because they are driven more gently and on dry roads. Since the tires are for sure 7 years old, replacement tires will be required soon. On the front drive Eldorados of that era, well for sure 1966-85, the front tire quality is very important. Have gotten rid of shimmy at highway speed on these beauties just by replacing tires. Of course usually an alignment, high quality shocks and road force Hunter tire/rim balance accompanies tire replacement.