The problem with Clark or other’s OD trans. is they use the third gear position for the OD location, so one goes from second to direct with nothing between, very difficult, even with a two speed rear, especially with a load, so be careful in considering similar OD trans. Have to weigh advantages of OD vs. stuck in second ‘til top of hill.

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.