There has often been variation in the amount of off-centeredness involved, but almost all are somewhat off of being exactly 180 degrees apart, so if there's no position at which both disappear from view, just get them to the place they both show the (equal) smallest bit of a hole still visible
If it's offset put the "close" side down towards the crank, and in any case, put it crossways as you can get it. It doesn't really matter - I have seen them with one hole straight up and the other straight down work just fine.
If you get a good combination of needle and spraybar, the stock parts work pretty well, even when it leaks air like a sieve. But I can't tell you for sure how to find which are good combinations or bad combinations without just testing a bunch of them.
Brett