I have a 81 Blazer K5, 38" tyres, 4.88 rear, 12bolt/dana44, NP208, 350ci and TH350. I was considering swapping the 350/350 out for 6.2/TH700. Is it possible to predict what kind of MPG I would get? Shouldn´t it be much better than with my current combo? I love the 350 but the prize of gas is around $4 for the gallon over here . It is would also be good not to have to travel with as much extra gas when I am traveling out of nowhere (my 30 gallon tank is not big enough). Jon H.