Ken,

Thank you for the extensive information you've provided!
I currently have Mercedes connectors but will look into the NAPA ones.

You discussed round vs. rectangular. Here's my story.

I followed my usual path of least resistance in my selection of 6' x 8" bulbs.

1) Round requires round cuts in whatever trim I would use. Rectangular should be easier, needing straight cuts. That's the theory, anyway. Trim work to follow in the spring. Headlights are installed now.
2) Quad rectangulars from early 80's 240 were considered first. I could not see how to fit them to my '89, due to lights too wide to allow for existing '89 grill. Only after installing both 6x8 lights did a friend suggest that by swapping in the horizontal steel plate behind bumper (full width of car, just below/in front of radiator support bracket, apparently requires drilling out 2 rivets), I could likely transplant a complete early 80's 240 front end. Worth looking into.
3) Dual rectangulars were addressed next, and worked out. Will save me money buying e-codes too! Though in a pinch, you could put e-codes in the hi-low location and low cost DOT for high beams.

I went after a Mercedes 6" x 8" first, but the base bracket was a monstrous plastic casting that really needs the correct M-B nose as a place to be fastened to. It would have been a bear to install. I pulled a very nice and workable set from an Isuzu pickup. It has four "feet" that need bolting to a flat radiator suppoort bracket, which the 240 has. I looked at many American small trucks but they integrated the headlight guts into either the rad. support bracket, or into a very large flat piece of sheet metal attached to said bracket. Not for me. I believe Toyota pickups may have a similar or identical headlight, if anyone wants to pursue this.

Trim:
Volvo 740 grills (two) will be trimmed to fill the vacant spaces left by the missing OEM fishtank lens. Grill spacing and format is nearly identical to the 240 version, and is more workable due to a different design of the plastic "bridging" under the diagonal slash. I plan to do cardboard mockups first so as to not wreck the grill stock. I plan to paint all grillwork black in the spring.
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Sven: '89 245, IPD sways, electric rad. fan conversion, 28+ mpg - auto tranny. 850 mi/week commute. '89 245 #2 (wifemobile). '90 244 (spare, runs).