My 142 is a 1971. The 1971 parts manual listed both bonded and gasket style glass in use on the 1971 cars. I don't know whether that was a market specific thing or a change that occurred mid way through the year. I don't recall an up to chassis # and after chassis # in the parts manual which is what is listed when its a mid year production change.

As I recall, the lip on the top of the dash with the screw holes is not very large. You might be able to work the edge of the gasket up enough to get a screwdriver under the edge of the gasket to access the screws. However, I expect that reinstalling the dash with the gasket in place would involve a much higher level of difficulty. You probably want to do the dash reinstall before you put the gasket back in.

When my car was repainted, the rear glass which is gasket mounted was pulled out for the paint job. As I recall, the glass went into the gasket fairly easy; but, reinstalling the trim into the gasket involved some magic with a cord. It was not a trivial exercise like putting the trim back on the bonded windshield. If you are not familiar with the magic associated with getting the trim back into the gasket, you might want to research that a bit if you are going to do it yourself.