It will have the headlight pull-back switch. My old '63 122 had it, as does my '63 PV.

The axle won't be a bolt in like it would be on a 67+ sedan/coupe (not wagon) but putting it in an early sedan is easier that putting it in a wagon. The suspension design is at least conceptually the same early and late, it's jsut that the early cars used different syle mounts on either end. Way back in the 80's, my Dad and I put a 142e axle in my '63 122s. I forget the specifics this many years later, but as I recall we used one arm from the later car as is, and just cut the other arms in half and spliced them back together with a 122 car end and a 140 exle end. (We also had to move the panhard rod mount from one side to the other, but you wouldn't have to do that with the 1800E axle).

Here's the early 122 sedan/coupe suspension:


And the 1800E suspension:


IIRC the #19 arm on the 1800E suspension worked well as is, fitting up to hte body mount on the early 122. Bt the #12 arm on the 1800 suspension had to be cut and spliced with the front end of the #1 arm on the 122 suspension.

I seem to recall a small blurb I saw somewhere a couple of years ago about someone (IPD???)making up a small batch of suspension arms to do that very task. At the very least, that sort of welding is failry contained, portable (you can cart the parts off to a welder if need be, with measurements on the finished length), and in the end you are using an unmodified car body and an unmodified axle. I'd use as little as possible of the 122 arm, however. That arm was made os stamped thick sheet metal, and I think they have been known to rust out and fail.
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'63 PV544 rat rod, '93 Classic 245 + turbo