Don't know the year of your engine, but for a D24 this is the factory procedure:
Use a new gasket when installing the pump, if the position of number 1 piston was accidentally changed while the pump was off, remove number 1 spark plug. Rotate the crankshaft and check compression on number 1 cylinder by hold- ing thumb tightly over spark plug hole 01' by installing a compression gauge in hole. When compression is felt by thumb 01' shows on gauge, continue to turn crankshaft until piston is on top dead center as indicated when the pointer points to DC on the vibration damper (Fig. 26). Turn pump drive shaft until the slot in the end of the drive shaft lines up with the cap screw holes in the mounting flange (Fig. 27). Then turn the drive gear one tooth counter-clockwise. Loosen the distributor lock screw and raise the distributor just enough to allow the pump to be installed. Tighten pump cap screws. With dis-tributor still raised, turn rotor as shown infigure 28 until it points to about "seven o'clock," move the rotor back and forth slightly to allow the tongue of distributor shaft to engage with the slot of the oil pump drive shaft. Install num- ber one spark plug and distributor cap. adjust timing as outlined in "Electrical Section."