I have had quite a few Heuers on various bracelets and I cannot think of a one that had absolutely perfect fitting end links. Possibly tolerances in production were lower back then but also these days collectors are also buying up vintage bracelets to match with a vintage watch and if those end links have been around fifty years they may be compromised in some way.
I own a Carrera 1153N from the original owner with original GF bracelet he bought fitted to the watch. FYI the fit of even those end links is not perfect, there is a very small gap between the top of the link and case, to be honest had never really noticed it until now and have had, and worn, that watch for years.
I tried to a while back to fit a GF with HLF end links to my Autavia 1163 and just could not get a decent fit as the angle of the links sat them up over the case. It was only after some research I found HLF were apparently for thicker 11630 cases. The HLD links now on the watch still leave a little gap to the 1163 case top, again not really noticeable, just a millimetre or so, but it is there.
I digress as there are obviously only the HLC end links for Cal 11/12 Carreras. Is the fit the same on both sides?, if not possibly one of the links got squashed in transit. I did have a similar issue with a set of Omega 633 end links and Seamaster 300, I bent the bottom half of the link outward to open them up for a better fit. I did the lower section so any damage would hopefully not be visible. It worked but they were Omega service end links, easily obtained again if I broke them. Not so sure about doing that to rare original GF HLC.
Not sure if any of that helps but just my experiences with end link fit.