Here is a excerpt from the Yahoo 1800list that say the base can short causing the light to stay on. I have not had the problem or investigated if it true. Since you just reassmebled them I would look at it.

Greg B.
1970 1800E


^The reason your lights stay on is because the metal fixture that holds
the bulbs is shorting out against the car body.....I had the exact same
problem and heres the fix (should it turn out not to be the switch or
the lense thing)......remove the fixture from the car ....use electrical
tape on the rear of the fixture.....purchase some small plastic wall
anchors.....enlarge the hole in the car body where the little fixture
screws connect and put the wall anchors in there..... put everything
back together and make sure that no metal part of the fixture touches
the car frame.....What I suppose Volvo did orginaly was the light pannel
was held away from the frame by the new pannel and there was probably a
fiber washer around the fixture screw to keep the thing from shorting
out...over time the pannel weakened and the fiber washer disentegrated
and PO's just screwed the affair tighter and tighter against the car
body till it shorted out and kept the light on...not knowing what was
going on the removed the bulbs.....let me know if it works.....they make
neat colored bulbs for these lights too.....