oil priming engine

I am about ready to prime up the oiling system in my 273 which is already installed in the car. Will I have any trouble getting my priming shaft into the oil pump with the engine in the car? I know to put a gauge on the block and rotate the crankshaft while running the priming drill with the valve covers off. I was told I should have done all this on the engine stand and I didn't, just wondering if I screwed up-----------------again--------------
DRO:)