Yes, the car will pass emissions, but only when it's warm. The AIR pump only operates while the engine is warming up, to reduce smog in the process.
You could find a solution to resetting the check engine light and tell the client all is well, and let her go on her merry way, but of course, you as a mechanic, are held to a high standard. If I were in your shoes, I wouldn't be thinking how to circumvent the law, rather, how to fix the problem the way it was intended to be fixed.
I think your only solution is to tell her to put the original head back on with the AIR pump, or fit the 190 head (which you failed to mention in your original post - hence the flak) while re-fitting the pump or don't fix it at all.
I don't think any reputable and responsible technician or mechanic on this forum would tell you otherwise.
'91 300E, 208k miles