Clark OD's are somewhat rare, just look everyplace you go, in the correct size trucks. If you go in a yard, they won't know what you are talking about, just figure out some excuse to get in there, look on your own. Clark parts are reportedly hard to get, so don't get one apart, broken, in pieces, etc.

'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.