I wouldnt depend on the gauge, but if you are getting oil at the rockers, you've got it primed OK. The gauge should be working, but it may be NG.

Make sure the battery is good, and also the positive and the ground connections. You'll need a fully charged battery for the starting, as well as the MSD. Prime the oil again before starting up, and be sure you have the dist. timing about right and gas in the carb bowls, so you dont have to crank it a lot to get it to start. You dont want to have to crank it a lot with the new cam in there! Get it to start asap and get the rev's up during the break-in(2000 to 2500, vary it up and down once in awhile) Watch your temp during break-in too, it can get really hot, especially if the timing is a little retarded. Good luck with it.