How Much Horsepower Required to Cruise Comfortably at 70 MPH?

I ran my 367 with an effective Final drive ratio of 1.97, and so 85=2000rpm, for 500 miles and it returned 32 mpgUs, with a 600VS that I had tuned specifically for the trip. Same car went 12.9/106 with a 750DP and street tires. If Ida had a TQ, I bet it wouldda done better and gone faster, without the carb swap,lol.