340 Engine Priming?
Having a buddy around for engine priming is a great idea. Have him watch the oil pressure come up on the gauge (you have installed a gauge, right?). Like everyone else says, you'll feel the resistance on the drill as the pressure comes up.
Once your helper sees pressure, have them rotate the engine twice to rotate the cam once. This will align the oiling holes on a LA engine cam. Have him check your oil pressure perodically and keep an out for leaks. Once that's done, rotate the engine so the #1 cyl is on 10 degrees BTDC on the compression stroke. Drop in your distributor drive gear so the slot runs pretty much fore and aft. Don't forget that it will twist clockwise as it drops in. Drop in your distributor so the rotor points to #1 and get ready to fire.
I always use straight water at first start up because I almost always find some kind of leak.
Hope this helps.