Don't know about the absolute pinnacle but just feel fortunate to have had a first series RS for well over quarter of a century. If not pinnacle (which for me is probably the 73 RSR variant of it) certainly it is at the camp just before the summit given the role the earliest 500 plus 500 911744 played in the Porsche racing history.
The early 911 744 were essentially the same for homologation certification before conversion to desired spec. In that sense an early 911744 model across the conversions makes a case for pinnacle
A purposefully designed limited edition recognisably 911-- every early 911744 aka Carrera RS part of the story that made the racing success possible by virtue of the factory's unconventional homologation /convert approach "madness". Access for customers to factory homologation special with deliberate motorsport element for buyers who didn't all need an actual race car. That balance of a road racer as hinted in the RS brochure in itself quite is quite noteworthy where sales/ marketing doubts met the motorsport imperative. Result: buyers got to choose their 911744 variant and Porsche got to comply with FIA rules to quickly develop a 911 competitive and successful 911 racecar that is for many the now the iconic longhood.
An RS does all things well, at one time being my everyday car taking kids to nursery, regular supermarket shopping and going to work but also holds it head up well even by more recent standards on road and great for spirited track driving if the mood takes. Nice to use on classic or touring leisure events with wife or friends. The M472 Touring package gave practicality -- no surprise most buyers eschewed the stripped out M471 and chose to pay more for usability. Sensible rather than looking like wannabe racers. Won 73 British championship rounds part of overall dominant win by model but driven to track in comfort still with radio eight track stereo and heavy hirschmann electric aerial. Lack of the wider arches and sensible comfortable interior Vs stripped out is ...less i got lost on way to track but enough elements of a purposful road race machine of that era. Rennsport design aspect in eyes of factory for the then top of range car "homologation special" In 73 holds up well. Even in early 73 the first series Touring version of 911744 was being called out as a "classic".
(As an aside some of the styling touches like flatnose once a must have racy styling touch for the man about town are out of favour for most these days; sometimes I wonder if the archly fashionable touches seen on many racer aping cars that are so fashionable to build today will fall out of favour and look somewhat dated and even a bit gauche in the fullness of time? The naffness of Magnus Walker adding little derivative touches as if adding little styling touches to create trendy jeans are one a case in point. The Carrera RS styling elements can be a bit much too Vs some more purelines but they are at least authentic Rennsport things as styling dept did them back in the day to work with the functional racing elements like ducktail.)
Even by September 75 -- the three years on from launch-- new Turbo didn't outclass it in real world performance to 90mph as shown below; actual figures taken by same magazine and using same test protocols.
On the track in the well supported races Porsche Club GB late eighties the RS was the tool even over these blown cars.
Earlier factory ST is maybe rarer but the fact the factory needed to up the game and box clever with homologation of 911744 in M491 RSR form to beat the competition when the 2.5 was noted to be struggling Vs competitors as observed at race by the embarrassed then new Porsche boss should not be overlooked. That was the spark for the model and change of plans to develop homologation special according to lore.
The pinnacle -- who knows -- some mentioned are rarer and some more expensive but the RS is the only car of many I've owned I wanted to keep -- it does everything I need of a classic car. Interestingly Gordon Bruce who was road test editor of a well known weekly chose RS as his long term car despite driving most cars around the early 70s in road test conditions. A 73 RS is often a cornerstone of knowledgable collectors some of whom have means to but whatever they like.
If "feels too modern" means all round competence and very usable classic in even in today's road conditions then it good enough for me.
The 73 Carrera RS when couched correctly using its 911744 model designation ( but an early example with the special touches: thinner body panels, first for roadcar different front rear rare wheels , 60 profile rear tyres, and the real aero effect of burzel/ front bumper, racing cylinder material use on roadcar to give capacity, gearbox details, forged front crossmember, strengthened rear suspension, even the plastic horn push that saved the weight of a packet of Cheetos etc etc). Things that were by design for this homologation special and certifiably part of achieving homologation of the model ith FIA; there is a strong argument for the 911744 being the pinnacle longhood! Kind of hits the Rennsport essence in a sensible way without all being actual factory racecars.
Spectrum of variants makes it relevant: supermarket nursery runaround to prototype beating capability in world class race events in era of longhood. Also last longhood foundation for Porsche motorsport success for many years thereafter - neither rarity nor being and actual factory racecar to me doesn't equate to pinnacle "model". Maybe that breadth of capability and track record of suces for the 911744 RS/R model does? If imitation is the best form of flattery well...lord knows how many Grand Prix White imitators exist of those just over 200 real genuine original 908 with blue decals paint code examples the factory built?
I'm very biased of course so if folks want to loan me the others to pursuade me I'm wrong then feel free
Steve