Fuel economy

I ran some numbers on different tires/gear combinations. I used the 10r80 gear ratios because they were already in the calculator.

32" tire 32.1" tire and 3.73 gives you:
70 mph is 1749 rpm
80 mph is 1999 rpm

32" tire 32.1" tire and 4.27 gives you:
70 mph is 2002 rpm
80 mph is 2288 rpm

33" tire 32.6" and 4.46 gives you
@ 70mph is 2059 rpm
@ 80 rpm is 2354 rpm

35" tire 34.4" and 3.73 gives you
@70 is 1632 rpm
@80 is 1865 rpm

35" tire 34.4" and 4.27 gives you
@70 is 1868 rpm
@80 is 2135 rpm


The 35" are 25 lbs heavier so even though the rpm is lower I would expect worse fuel economy. Based on that I will put 33" (32.6") on whatever I buy if it doesn't already have them.
So my question is, how much do you think 350 rpm will effect fuel economy? I would like a Badlands with 4.46 but it would run at 2354 rpm vs 1999 rpm for a OBX.