One can also use ZF 5 and 6 speed trans.' Need to get familiar w/ them first. Direct trans. are more plentiful(NP540 for example) and less cost. One might find a Brownie that would work well w/ either a 4 or 5 speed, direct trans. 5500 and 5800 series Brownies would work fine, there are smaller Brownies too, mainly in farm trucks. Some depends on how hard you wish to work your truck.

'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.