about those 123 euro lights..
As far as i know they always come in pairs, either both sides level-adjustable by vacuum or as a pair of non-adjustables. I'll check the euro 123's around here to be sure though. Maybe you have a mis-matched set?
BTW, which euro lamps do you have, the early ones with the two round reflectors or the later ones with square reflectors?
Sorry, can't help you out with the gaskets.