If it has 17" tires, 70 mph is not all that fast. In 1962 Texas raised the speed limit from 60 to 70 and of course had to lower it to 55 in the mid 70's. We drove the speed limit and more in those days. We just disregarded the noise and vibrations. Engines don't fly apart when operated in the 3,000+ range, even though they may sound like it. As long as you have a good radiator to keep them cool, a stock carburetor won't give them enough gas to over rev them to dangerous levels. For us old geezers who got their drivers license in the 50's, having to slow down to 55 in the 70's was a real pain.
