Hey thanks for that reply! So it sounds to me like you are saying the air pump is not a critical issue as far as drivability and how the engine will run. If that's the case, then I'm not going to all the trouble of swapping the heads. I was going to go ahead and bolt the metal tube to the top of the engine and just remove the rubber o-ring/gasket so the air can just blow out around the tube (for cosmetic purposes, as you suggested).

One reason I was concerned, was that I read somewhere (Volvo Speed Site, I think...) that if the air pump sets codes in the ECM, then fuel trim is disabled. (Here's the site link: http://volvospeed.com/Repair/airpump1.php ).

That sounded like it might cause performance/driveabilty problems. But as I read more, at different locations, I found several posts where people acted as though the air pump not working really made no significant difference in their car's performance.

So I'm leaning toward just going ahead and installing the engine with the manifolds swapped, and not getting overly worried about the air pump.

Thanks again for your reply!