Bart, I hope its a big piggy bank. As Mike points out a lot of things were changed on W113s, especially the later versions sent to the US. When I had the body work done on my July 1970 build I had them weld patches for the holes for the side markers and when I install bumpers they will be without the bumper guards. I will soon be installing an early version of the blue, red and gray heater slides. I'm in the process of working on the euro headlights too. One change that won't be made is removing the headrests since my wife views them as a must - and she's surely right about that.
I would like to "shiny up" some of the trim that was given a matte finish required by US DOT but still working on that.
Since I ended up practically building my car from the ground up, I've done a few other things like vented front brakes, not that I will be driving it that hard - just was easy enough to do.
I'm not really a purist, but I do enjoy the cleaner look of the earlier cars and everything I've done can be reversed if that's a subsequent owner's desire.
If you end up switching over to the euro headlights check out the Technical Manual and some earlier posts. You will have to unplug the wiring connector at the headlight and rearrange the wires in the connector to match up with the euro headlight electricals. Not hard to do.
Lee