Not sure when I'll be able to undertake this retrofit I've been planning so I've decided to share all the info I've gathered in the hope that someone else might want to give it a try.
This is intended for a 240 with pop-up headlights, but it could used for anything with 5x7 sealed beams.
I'm big into OEM styling, so it's been a challenge to come up with something that satisfies the lighting nerd in me but also looks like it could have been OEM. I really dislike the look of a projector retrofit in plastic clear lens 5x7 housing. IMO, a fluted glass lens is key, think R32, Silvia, or E30 projector headlights.
Initially I found these rectangle projectors from Hella. They are somewhat known within the VW crowd.

HELLA 1BL 005 380-011
The shape didn't seem quite right... they are very squared off. The depth was also huge... way too much to fit in an S13.
Recently I came across another set of Hella's from a MAN passenger bus. A more traditional 5x7 shape and depth that I can work with.

HELLA 1BL 005 740-091
Profile Shot:
Naturally there is zero information on the internet regarding these, but I was able to gather they are low beam only. This is why a retrofit is necessary, a bi-xenon projector needs to be swapped in to retain high/low function.
I was able to track down this photo, which shows that the stock projectors are literally screwed in from the back, making them prime retrofit candidates... the glass wouldn't even need to be separated.
That's all I got for now... thoughts?