ratio gear problems

[lamarrana32]

Hi, i have chevy pick up 69 c10, with motor 350, and transmission 700r4 (originally has manual transmission), the gear ratio is 3.071, but the max. speed is 55 MPH at 3200 RPM with 4 th transmission shift and waste a lot fuel, im thinking the problem is the gear ratio and i want to chage for a chevy 1985 gear ratio 2.56 (43-14),

This modification improve the speed in the road? what do tou think?

thank you for your help.

regards.