I bought a shelving unit that has 2 openings in the back for hanging. Problem is they're 44" apart. Obviously this won't hit studs evenly. What can I do?
Can you post a picture of the unit and how it's supposed to be mounted?
Normally, a cabinet meant to be hung will have strong backs across it's width at the top and bottom. As long as you screw through the strong backs and into studs you should be safe
Another method is a cleat along the top with a mating cleat that is attached to the wall. Hang the cleat, hang the cabinet off the cleat, add a couple screws through cabinet into studs for security and you're done.
Another method still is hanger rings mounted to the back of the cabinet. You could locate the studs, position the cabinet to the wall and mark the stud position on the cabinet, then move the hanger rings to where they'll do some good.
As you can see, just guesses without knowing more about your cabinet.