Could be 3.55 or 4.10
near the coil on the manifold
It is part of the engine computer, behind the battery.
it is printed on the data plate. Mine has an A833 manual 3 sppeed with overdrive
It is on the top of the pump on the front of the trans inside the bell housing.
On a 1988 D150 w/ 318, it is driver's side front of vehicle.
to the right of the master cylinder on the driver's side fire wall