Not sure if the 328 engine mount is the same as the one on my 325, however when I reinstalled my OEM headers, there was barely enough clearance to put it back in. It has two bolts coming out of the center, one faces the top and the other towards the bottom.
The only solution I found, without jacking up one side of the engine beyond my comfort zone, was to disassemble it. I mounted it onto the engine first, positioned the top bolt in the hole, and used a small lever to insert the bottom bolt. At this point I was essentially using my one hand pushing up on the engine, and the other on the lever (guiding the bottom bolt in its hole).