In 51' there were only lever shift PTO's on the floor if your looking for originality.
Cable shift PTO's didn't come along until the 60's. Most floor shift lever assemblies were supplied by the hoist manufacturer and had both a PTO and pump control lever that pivoted on a steel bracket that mounted to the floor. That is one reason so many of the floors rusted out. Transmissions with a drivers side PTO were a particular nuisance since they would have the controls on the left and directly in the drivers way.
Most installers, including yours truly, of cable controls put them under the dash near the drivers door or often through the floor beside the seat as a direct pull operation. I always preferred the LH under dash location because it would allow the operator to stand outside the cab and see what he was doing. This was the best location since many of the older trucks had small mirrors or occassionally none at all.
