I may have missed an earlier post, but have you removed the lens to see what type bulbs & sockets you have? Despite the manual Specifications, I've seen very few early '80s with the small 5 watt #67 clear bulb in the upper socket. And I suspect these were used with the Amber lensed units (76-79 or so). The manuals seem not to have changed when the lenses did.

You are right, with the clear lens, you should find a socket configured for a dual-filament bulb, the AMBER #1157NA. The interesting thing is that only the 5 watt filament was wired. My thought was that they might have gone to the 2-filament socket to use the 21 watt part for DRLs in Europe.

So that's what I did on 3 or 4 cars we had -- up to an '86. Added the needed contact & wired it thru normally closed relay points from a Key-On power source. Then picked the relay from a parking light fuse. Worked great. Much better than those Daytime Infuriating Lights on most cars now.
--
Bruce Young,
940-NA (current)
'80 GLE V8 (Now gone)
'83 Turbo 245
'73 142 (98K)
'71 144 (track modified--and going to be crushed unless...)
New 144 from '67 to '78
Used '62 122 from '63 to '67