All those rear ends whether single or two speed only come with low or lower ratios. Is your truck '47 first or second series? A NV-4500 tranny will work, might have to drill and tap mounting bolt pattern in the front of 4500, easier to do if trans innards removed. Another option is a 'Brownie' 3 or 4 speed aux. trans if you have enough driveline room. Next size tires might help, try to get tubeless wheels and tires.

Then you have to be sure your brakes and steering are up to the increased speed.

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.