Trick or tool to help line up 48 splined crank arms
If your bearings are decent, just take the non-drive pedal off and let the pedal weight pull the other side down, or slowly let it fall from slightly off center. This is how I could tell with my Bullseye cranks, besides hopping on and trying to pedal it. If that doesn't work then I'd try tying a heavy weight or looping a paint can around one of the pedals close to the crank. 

You're looking for a 7.5 degree distance, so on 185mm cranks that's 24mm or nearly and inch of diference between splines. Weighting the opposite side enough should make it clear. I then took some nail polish and marked both the crank and axle so I didn't have to play this game again.