It will be very similar to the 500SEL of the early 80s. In Europe MB often sells models that never make it to US shores unless cars originally sold in Europe are brought back by someone like your friend. The difference between the 500SE and 500SEL is that the SE has 4 inches less legroom in the rear. The L in SEL stands for long and if you put an SEL nest to an SE it is pretty obvious. The extra lenght in the SEL is all in the rear doors. North America got both the 380SE and 380SEL, but only the 500SEL. There will likely be a few mechanical differences between the European and American version 500 series w126, but I am not familiar enough with them to go into detail.

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Jason Priest
1999 E430
1995 E420 - retired
1986 420SEL - retired