Info from Standard Catalog of Imported Cars basically confirms all this with a bit more detail.
- only a single SL version sold in US in any given year, so no parallel choices
- no sign of any US 420 SL ever; the only 420 listed was 420 SEL 1986-92
- SL sequence was
[1] 1972 only - 350 SL (but it had 4.5 engine)
[2] 1973-81 - 450 SL (and SLC)
[3] 1981-85 - replaced by 380 SL (and SLC, but that disappeared for 83)
[4] 1986-89 - replaced by 560SL
[5] 1990 R107 replaced by next gen SL.

Strange, I added comment there, we'll see if someone finds an explanation. Possibly not a true US model.

If that's a 420SL then it can't be made for USA, since there was never a 420SL in the USA.

Is it right to apply that to all models?
We have at least one exception: https://www.imcdb.org/vehicle_1668545-Mercedes-Benz-420-SL-R107-1986.html

560 SL:

https://www.imcdb.org/vehicles.php?resultsStyle=asImages&yearFrom=1986&yearTo=19- 89&makeMatch=2&make=&modelMatch=1&model=SL&modelInclModel=on&modelInclChassis=on- &mk=&origin=&madein=&madefor=CDN&role=

https://www.imcdb.org/vehicles.php?resultsStyle=asImages&yearFrom=1986&yearTo=19- 89&makeMatch=2&make=Mercedes-Benz&modelMatch=1&model=SL&modelInclModel=on&modelInclChassis=on&mk=&origin=&madein=- &madefor=USA&role=

450 SL:

https://www.imcdb.org/vehicle_580556-Mercedes-Benz-SL-R107-1974.html
https://www.imcdb.org/vehicle_574107-Mercedes-Benz-SL-R107-1974.html
https://www.imcdb.org/vehicle_557088-Mercedes-Benz-SL-R107-1974.html
https://www.imcdb.org/vehicle_435815-Mercedes-Benz-SL-R107-1974.html
https://www.imcdb.org/vehicle_444775-Mercedes-Benz-SL-R107-1974.html
https://www.imcdb.org/vehicle_647547-Mercedes-Benz-SL-R107-1974.html
https://www.imcdb.org/vehicle_1051677-Mercedes-Benz-SL-R107-1974.html
https://www.imcdb.org/vehicle_1481056-Mercedes-Benz-SL-R107-1974.html
https://www.imcdb.org/vehicle_1450013-Mercedes-Benz-SL-R107-1974.html
https://www.imcdb.org/vehicle_1912068-Mercedes-Benz-SL-R107-1974.html
https://www.imcdb.org/vehicle_1993711-Mercedes-Benz-SL-R107-1974.html
https://www.imcdb.org/vehicle_2028918-Mercedes-Benz-SL-R107-1974.html
https://www.imcdb.org/vehicle_682595-Mercedes-Benz-SL-R107-1975.html
https://www.imcdb.org/vehicle_1495110-Mercedes-Benz-SL-R107-1977.html
https://www.imcdb.org/vehicle_1639592-Mercedes-Benz-SL-R107-1977.html
https://www.imcdb.org/vehicle_2021435-Mercedes-Benz-SL-R107-1977.html
https://www.imcdb.org/vehicle_260840-Mercedes-Benz-SL-R107-1978.html
https://www.imcdb.org/vehicle_1969589-Mercedes-Benz-SL-R107.html
https://www.imcdb.org/vehicle_1853565-Mercedes-Benz-SL-R107.html
https://www.imcdb.org/vehicle_856089-Mercedes-Benz-SL-R107-1977.html
https://www.imcdb.org/vehicle_1454404-Mercedes-Benz-SL-R107-1975.html
https://www.imcdb.org/vehicle_587248-Mercedes-Benz-SL-R107-1977.html
https://www.imcdb.org/vehicle_1214217-Mercedes-Benz-SL-R107-1977.html
https://www.imcdb.org/vehicle_1299234-Mercedes-Benz-SL-R107-1977.html
https://www.imcdb.org/vehicle_1359156-Mercedes-Benz-SL-R107-1977.html
https://www.imcdb.org/vehicle_982948-Mercedes-Benz-SL-R107-1974.html
https://www.imcdb.org/vehicle_2116189-Mercedes-Benz-SL-R107-1974.html
https://www.imcdb.org/vehicle_456888-Mercedes-Benz-SL-R107-1974.html
https://www.imcdb.org/vehicle_1498748-Mercedes-Benz-SL-R107-1974.html
https://www.imcdb.org/vehicle_839660-Mercedes-Benz-SL-R107-1975.html
https://www.imcdb.org/vehicle_1487793-Mercedes-Benz-SL-R107-1975.html
https://www.imcdb.org/vehicle_169377-Mercedes-Benz-SL-R107-1975.html
https://www.imcdb.org/vehicle_629085-Mercedes-Benz-SL-R107-1978.html
https://www.imcdb.org/vehicle_1929098-Mercedes-Benz-SL-R107-1977.html
https://www.imcdb.org/vehicle_27496-Mercedes-Benz-SL-R107-1978.html
https://www.imcdb.org/vehicle_27043-Mercedes-Benz-SL-R107-1978.html
https://www.imcdb.org/vehicle_86484-Mercedes-Benz-SL-R107-1977.html
https://www.imcdb.org/vehicle_762595-Mercedes-Benz-SL-R107-1977.html
https://www.imcdb.org/vehicle_759766-Mercedes-Benz-SL-R107-1977.html

It was not forgotten: these were my question: are they just lookalike clone or really a local build of the same vehicle.
I suppose that if they cooperated for many other vehicles, back then there were already agreements on these vehicles.

For me, these are Nissan models, rebadged following the joint venture with Nissan.
https://www.imcdb.org/vehicles_make-Dongfeng-Nissan.html
there was a forgetting for those:
https://www.imcdb.org/vehicles_make-Dongfeng_model-Ruiqi.html

I don't know what origin should be chosen for these copies. If they just copy the style, I don't know if the source origin should be kept. But if they recreate the same vehicle indeed it would be logical to keep the origin.

For there:
https://www.imcdb.org/vehicle_2101087-Dongfeng.html
https://www.imcdb.org/vehicles_make-Dongfeng_model-Duolika.html
https://www.imcdb.org/vehicles_make-Dongfeng_model-EQ+1118+GA.html
https://www.imcdb.org/vehicles_make-Dongfeng_model-EQ+1146.html
https://www.imcdb.org/vehicle_370200-Dongfeng-EQ-153.html
https://www.imcdb.org/vehicles_make-Dongfeng_model-EQ+2102+GAJ.html
https://www.imcdb.org/vehicles_make-Dongfeng_model-EQ+2162.html
https://www.imcdb.org/vehicles_make-Dongfeng_model-Ruiqi.html
https://www.imcdb.org/vehicle_535644-Dongfeng-EQ-Series.html
https://www.imcdb.org/vehicle_1038334-Dongfeng-EQ-Series.html
Origin: Japan
Built in China.
Made for CN.
these are copies of Nissan trucks (Condor/CM-Series or Navara).

For all "Dacia Duster Mk3", chassis code is "DJF".
https://voitures.centralepneus.fr/pneu/dacia/duster/duster-4883/40292

For all "2018+ Alpine A110", chassis code is "AEF".
https://www.imcdb.org/vehicles.php?resultsStyle=asImages&yearFrom=2017&yearTo=&makeMatch=- 2&make=alpine&modelMatch=1&model=a110&modelInclModel=on&modelInclChassis=on&mk=&origin=- &madein=&madefor=&role=
https://en.wikipedia.org/wiki/Alpine_A110_(2017)

I think you’re right, let’s leave it like that and we’ll see later if things evolve.