Dear James,
My 2 cents advice: don't!
Theoretically the swap is possible but in practice - rather not.
As a full member, who you are, 2 years ago or so I wrote a seat article and got that published in the PagodaWorld.
I am sure, I am confident you haven't read it - too uninteresting for you.
Certainly you are also not interested in my advice... possibly.
Probably you should read it at least partially now - it helps understand your problem here.
To make a short story long...,
all seats younger than very early 230 SLs (1963's so to speak) are two-handed: left and right side seat. While (as Alfred mentioned) the backrests are always identical left and right
within a given car, the seat cushions
are not. They are laterally reversed,
with the outside of the seat cushion being wider than the inside (towards the wooden tray).
Now, you
can disassemble seats and rails and hinges/incline mechanisms to change passenger's and driver's side parts forth and back; however, you will usually always see that an ex-passenger seat is still a passenger seat due to its different form.
Have a look to the seat cushions of your 2 seats, and you will understand what I mean.
Well...., actually...,
after removal of your (perfect leather) seat covers you "could" even change the differences below there ..., will say the rubber-horsehair upholstery and even "change" the spring cushion,
but I dearly recommend not to do so.
Usually, after some 40#+ years the springs, especially the ones in the seat cushions (the so called Nosag wave springs), have sagged and just need to be replaced by new ones.
Pretty similar with the springs in the backrest. There, the flat steel springs are usually broken, and better do not weld them but get the broken pieces replaced.
There are good upholstery shops who can do that. Ask Stick or Roger Edwards Motors or other highly recommended sites for some good locations here close to your home. Otherwise I can recommend two excellent sites for you in Germany ....
But I think after a 40+ years period, you just need to take care (or let take care) of the non-visible parts of the seat as well and get those professionally repaired.
It is a h-u-g-e difference then . Do it (
I did it on my car - what a difference ...!)
You will love your car again, it's a huge difference in driving comfort - especially on long trips (European Event 2018 and so), not only for you but also for Tamara.
My 2 cents ....
Achim
(with repaired seats)