Have you seen the wire that supplies current to the compressor clutch? It can't be more than 5 or 10 A unless there is something I haven't taken into account.
The pusher fan in front of the radiator is probably the largest OE current drain outside the lighting. I have Hella H3's in place of the 5-3/4 fogs. std 55 W bulbs. ANd I use Hellas below the bumper on one of my W123's. No big deal, I really dislike using 100 W bulbs and people that use them are on my spit list too
I am going to install an 80-0-80 amp gauge in my '79 300TD when I get the time to lash it in and then I can see firsthand how much current it needs. I will be shocked if I don't have at least 20 A left to run puller fans (I have been wanting to get rid of the clutch driven fan for a long time)
PS Thanks for the link to dc controls! I appreciate that!