The Rear axle in question is in a 1989 2wd dakota. My aliment guy said there was some thing wrong(bent)with it. If you use your hand to measure between the front of the tire and the wheel well lip their looks to be a 1/2" difference side to side. I bought this truck used and I know the guy replaced the rear end. Is there some way I can check to see if the housing is bent?

Straight edge from side to side???

To check everything, jack it up and make a mark in the middle of the tread of the tire. Measure between them with both marks at the bottom (6 o'clock), 90 in front ( right side at 3 o'clock), and 90 in rear( right side at 9 o'clock). You can use a plumb bob if the tape won't clear. If they are all the same, nothing's bent. If they are off, the wheels, axles or the housing can be bent.
To absolutely check the housing, you can take out everything and install a housing narrowing fixture. You may be able to get creative with a laser too.

You can't really trust the body on such a measurement.
Measure from the face of the axle tubes to the spring hangers, fore & aft, each side; make sure the rearend's square with the chassis.
Drop the driveshaft, support the rear axle, spin each wheel and see if they're difficult to turn.
With the rearend assembled & in the truck, you'll need a way to mount a straightedege so you can measure between it and the axle tubes, so that the straightedge extends beyond the pumpkin.
Maybe Dr.Diff here has another method.

I just jack the vehicle up and mount two bare wheels (no tires). Then I measure from the outside of one rim to outside of the other rim in roughly four places, front, back, top, bottom. Then I rotate the wheels about 1/4 turn and repeat. Do this four times. Take all four readings at each spot and average. The difference between averages is the amount of bend in both planes. Works better with a helper.