"So let me get this straight: you're concerned about originality/history when you've got a hot-rodded flat six in a replica of a car that never had a six? Ironic."
IF I may offer an explanation: for whatever reason, as you have suggested, WEBERS or carbs became a favored choice in the 70s after the factory MFI cars either proved TOO DIFFICULT for the average garage techie to tune OR was a cheaper pursuit. It appears that you have the savvy and skill to achieve what others could not back in the 70s. It appears that a whole bunch of guys were into the 2.7RS setup and went with WEBERS. Whether easy, cheap, or more horses....they became a state-of-the-art choice for decades.
The flat-six WEBER following is still quite strong, for whatever reason(s) and whether twin plug or crank fired, it still lives on amongst many today. My IM6 was built to spec by the ORIGINAL OWNER in the spirit of that ERA by SUPERTEC PERFORMANCE, one of the premier builders of 2.7 variants on planet earth. Mind you, the car was built in 2008 for over $100K AND the owner could very EASILY have picked an MFI/CIS/CARB set up that fancied him...but he chose WEBERS.....in the spirit of his historical perspective and choice, now MINE!
So YES...ORIGINAL to his build/now MY CAR/ in the spirit of 70s HISTORY. IRONY, yes, but I find comfort in that spirit AND that mint WEBERS(3 barrels as per 2.7) go for up to 10K today. Of course one could have a custom EFI with magnesium/titanium throttles made for 25k...NONE of which was around back in the 70s either. FOLKS are still building 2.7s with WEBERS just as many 914/VW owners have trashed their MFIs for CARBS. I choose to have a 12 volt battery in my FAKE PORSCHE like thousands of others despite the fact that they were NOT original either along with transistor ignition, etc.
Despite the fact that the ZENITHS and SOLEXES were considered crapola by the PORSCHE-O-FILES and that 3 barrel WEBERS were originally a FERRARI choice for their six cylinder DINOs, they do hold a FIRM place in FLAT SIX LORE....
Right now I'm not up to twin plugging and EFIing my car for another 25K despite the amazing performance upgrade with its state-of-the-art tune.....indeed a GREAT spec for a 2.7 as you indicate.
IRONIC....indeed