We are replacing the mass air flow sensor on a 1996 aerostar. (Unfortunately we got a rebuilt one before finding out about cleaning them.) I want to test the new one to make sure it's good. I haven't been able to find information about what the ohm rating is supposed to be or which pins to test.

Help appreciated.

Cleaning isn't always an effective repair but it's often worth a try.
Test parameters for your Ford vary somewhat but they don't specify the resistance but would rather interpret voltage feedback at the ECM into gm/sec calculations.
For example, at approx 0.94 gm/sec the ECM would "see" about 0.34VDC and at approx 88.91 gm/ sec the ECM would see about 3.9 VDC.
Measurements should be done with a minimum 10M Ohm DVOM (adequate) or high impedance o-scope (preferred).