Many 2 speed rears are pretty low, so check carefully on the ratio before you get one. I replaced a 6.5 single speed with a 4.13 two speed, made a tremendous difference.

I agree with Sweepleader, most light truck 5 speeds have that big gap where 3rd used to be, most originally came with a 2 speed rear which would help. I put brownies in where driveline length allows.

Ed


'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.