460 operating RPM's ? C6 ratio's
 

I have a 1984 E350 RV with a 460/C6 combo. It only has 36,000 miles so it runs great but it is geared for the 1984 speed limit of 55mph. It has a 4.1 rear. Are the ratio's in the 1984 E350 C6 trans 2.46 (1st) -1.46 (2nd) - 1 (3rd) as I have seen listed. ? I cannot beleive I was only turning 3100 rpm's when I went on vacation and tried to cruise at 65 mph. This gets me 6.7 mpg.
Or is 3100 rpm maximum for the 460. I really expected to find the rear to be a 5.1 and figured a change to 3.54 would be a nice change