Hello John,
You have got already a few thoughts by the others what to consider before selecting headrests or not.
1) Your trimmer Bob really seems to know nothing (!) about Pagodas; I highly recommend to choose someone else. Someone who is familiar with the proper choice of materials, specialities of the Pagoda interior, etc. Your Bob seems not to know what he is talking about.
-> My 2 cents: look for someone else with a lot of proper experience on Pagoda interiors.
Nothing is more annoying than throwing a lot of money in a trimmer's bin and get a result that is maybe of correct technical quality but has plenty of wrong and lousy details (and knowledge) that every fellow Pagoda owner will immediately recognize and point on on your car. Wrong vinyl or leather, wrong colo(u)rs, wrong stiching, pipes, perforation, incorrect carpet (yours should have Tufting carpet) etc. etc.
The old rule holds true here again ....: do it once, do it right.
2) Headrests or not is basically a question of your personal taste, not more or less.
This depends on whether
you like them (or not) or whether you
want them or not, etc.
Sure they distract a bit the slim line of the Pagoda but you don't see that while _you_ (!) drive;
and basically they are period-correct.
3) Our Pagodas (i.e. the 280 SLs) were among the first cars Mercedes-Benz offered with (kind of) safety head rests. All cars before (e.g. older 108's 111's or so until early 1968) had only neck rolls (as an optional extra) which were solely a comfort feature for resting/sleeping passengers but by no way a safety feature.
Our cars (i.e. W 108 - W115) were the fist with headrests, and only from 1968 onwards. So, Mercedes' knowledge on them was still at the beginning in these years !
The first 280 SL which received HR was serial no. 004052. From then onwards all US-version 280ies had headrests standard; all other non-US Pagodas only at special order.
Sadly our "cabriolets" have got a low silhouette line (which is chic !) but that means that the seat's backrests are also low profile and that is of course negative in view to the safety feature headrests just in general.
Today's modern cars have much higher silhouettes (or belt lines) and as such much longer back rests on their seats and thus also headrests.
You can't achieve that with the Pagoda seats.
4) Thus, the Pagodas hare-style headrests provide a bit of safety (or believe in safety) but you need to adjust the height a bit more than on usual modern seats, otherwise they're completely useless and you can better pass on headrests. See the picture.
Often it are especially the beloved wives who would not want to accompany you anymore without a minimum of today's safety features, and seat belts and headrestraints are the least of that. This is especially important for today's younger wives ...
5) Of course headrests do influence your view backwards; pretty much in the same way as this does in modern cars.... or bit less I would say. But I would also say that is not really a drawback of the Pagoda's design. You'll certainly have enough view to the rear when parking in, even _with_ headrests; much better than with modern cars.
Consider please, you also don't have reverse parking sensors or even a fully autonomous park-in system with our cars, or do you?
So, in summary it is up to you to choose headrests or not.
During my about 30 years of Pagoda ownership I made the following observation:
The older (owner) folks can still often rather live without headrests. Their old 'Ford Flacons' (or whatever) in the old days also came without headrests. The owners never missed the non-existing headrests back then since nothing serious ever happened; so why should there today?
The younger folks rather tends to retrofit them (if not already in place) due to a request of a minimum of safety features which are absolutely standard today - and anyway these were available back in 1969 or so. Same on safety belts etc.
Only ABS and airbags is not as easy to be retrofitted on our cars ....
Summary 2:
If you now redo your interior, 2 more recommendations from my side:
a) Choose someone else than 'trimmer Bob'. He is not knowledgeable enough on Pagodas
Go instead with this Bob:
b) Get your car without headrests but have a set of headrests done at the same time (with the same leather etc.) .
Then you have a "matching" colo(ur) system with your headrests if you once decide to retrofit.
c) By this way you can still decide to put them in at a later timepoint or not.
And one last recommendation:
If you choose to go with headrests (at least on your shelf) go and look for the correct ones (like the ones on my picture).
Only the MB headrests up to 04.72 (April 1972) are correct; all later ones have a more square cut profile and look incorrect and not accurate in a Pagoda.
Good luck !
Achim
(heavy headrest collector)
(1964 230 soon with 1969 headrests) 
