Oliver did indeed offer an air clean above the hood kit. Now we were diesel minded and I probably ever did a handfull on gas 88 tractors. The Oliver kit is ugly and went through the grill. On the 88 gas tractors we  did we put the pipe straight up from the air cleaner. On your hydra-lectric: Does the unit have a filter? Does your tractor have disk brakes? If so, can you see a self locking nut in the center of the bull pinon. On the engine is there a square pad cast in the block under the distributor where a little square plate is and the plate could be removed and a Hobbs (at that time) hourmeter be installed. That change was made in early 1952.