I drove a 1958 Chevy Delray coupe for several years- - - - -It had a 235 a, 3 speed, a 3.70:1 rear end and relatively low profile 14 inch tires. I had no trouble at all cruising at 65-70 MPH, and short runs to 85 or so were not impossible. You should be able to cruise comfortably at 55-60 from New York to California.
Jerry