You have the oil pump driveshaft snapped into the new cam synchro, right? It should have come out with the old synchro, and you would have swapped it over to the new one. If so, try what I said above. With the synchro/driveshaft assembly sitting in the hole (as far as it will currently go), rotate the crank back and forth a little to see if you can get the driveshaft to line up with the pump and drop into place. If that doesn't work, then yes, you'll need to pull the oil pump, install the synchro/driveshaft, then reinstall the oil pump.