You can read about e-codes at danielsternlighting.com
and also at rallylights.com
I'll put what I can here.

Here in the US the headlight beam pattern is defined by the USA DOT regulations. So far as I know the Canadian regulations are referenced to copy the US ones, or at least for the most part.

The European countries have their own set of regulations that define a beam pattern that's for many of us far more effective. Low beam has a very sharp horizontal cutoff so 1) little or no light is wasted up high where it does not help you and 2) the lower area can be lit much more brightly since that light will not blind oncoming drivers. Consequently I am able to run 100/80 watt bulbs in my setup (high/low) and have not had other drivers express any irritation with the 80W low beams. Starting at the center point of this horizontal cutoff, the cutoff line angles upward to the right so that pedestrians and roadsigns etc. at the side of the road are illuminated nicely.

High beam is more of a pencil beam than the USA one; it illuminates far down the road very efficiently and has a slight spillover to the sides so you can see the sides of the road for a reasonable short distance.

My son bought a 2005 Hyundai (USA market) which apparently has a revised DOT low beam pattern. I don't know what it's called but it is a sharper horizontal cutoff than I've seen on earlier USA cars but not as distinct as the Euro ones. And it's flat, without the rising illuminated area off to the right. Does not really allow higher wattage bulbs as the system is plastic.

"Sealed beam" bulbs like those used on '85 and earlier 240s are easily replaced with e-code reflector housings. They were/are made for many European market cars. Those reflector housings fit just like our sealed beam bulbs do. They take an H4 bulb. Stern and RallyLights sell them in a variety of wattages and colors; I think regular parts stores may have the basic 65/55 watt types. If you buy Cibie or Hella brand housings they are made of metal and glass so will tolerate bulbs as strong as 130W. There are also newer design "composite reflector" versions with a beam pattern that's even better than what the glass/metal ones offer, but you're limited to basic standard wattage as the higher wattages get too hot for the plastic.

Those housings plus bulbs will usually run $100-140 per pair. Somewhere around there. For a 4-lamp car like yours you can just do the outer housings. That way you have e-code high and low beams from those two housings. If you spring for another pair later (the inner two), you'll have a total of four e-code high beams for those rural roads.

From '86 forward the 240 (USA version) used a dedicated headlamp housing accepting small 9004 bulbs to be inserted from the rear. Around that era most or all manufacturers changed over to that basic concept. USA cars got the USA-DOT beam pattern. The Euro version of those cars had a similar headlamp (glass lens, I believe) that gave the Euro beam pattern. You can get those for the 240 in the USA; we usually call them Eurolights to differentiate them from the bulb-replacement type that I described above. Cost is several hundred dollars, that includes replacing the turn signals which fit the eurolights. You have to hunt a bit for suppliers; there are occasional threads here discussing sources.

For the older sealed beam replacement type setup like on your '83 keep these two points in mind.
1) The "pinout" for your 4"x6" bulb's rear connectors is not the same as the pinout on other similar bulbs or the H4 bulb either. But no matter, Stern and RallyLights both provide the adapter to connect the terminals to the wires properly. That is, the H4 bulb has a 3 blade connector that looks just like the connector on the USA bulbs - but the ground wire is in a different position, etc. for the other wires.
2) The euro reflector housing is a bit deeper than the USA bulbs. At least it was on the 6"x8" ones I used on my car. I'm sure the pre '86 240s have enough room for them but if you're hacking your own from miscellaneous junkyard parts like I did, you may have to pay attention to rear clearance issues.

My installation? '89 240 came with the big plastic lenses. They got very very cloudy. I found decent 6" x 8" sealed beam headlight "buckets" on an early '90's Isuzu pickup and transplanted them. It was a lot of work (dozens of hours) and I'm not sure I'd do it again. Getting them installed and wired was a job in itself but fabricating decent trim was tough. It still looks home made but at least it's not ugly.
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Sven: '89 245 NA, 951 ECU, open-front airbox, E-fan, 205/65-15's, IPD sways, E-Codes, amber front corner reflectors, quad horns, tach, small clock. Wifemobile '89 245 NA stock. 90 244 NA spare, runs.