I dunno guys, there is no 'right' answer. To be honest I think we are overthinking this a bit. (I'm including myself amidst the guilty.)
A fact though, is the early case motors cost a lot more cash to get and get them up to snuff...$2-5,000 pretty easily to get the expensive sandcast case and do all that machine work that Porsche incorporated into the later 3.0L+ castings. For me, my money, to spend extra cash and get less power,....I would rather not. For cool factor yes maybe the 2.6/2.7SS is worth it. I think they are thoroughly cool and I think the 2.7SS is the ultimate expression of that 66mm crankshaft. But I am not a person that wouldn't miss $5,000 in my checking account.
That's why I mentioned more about application...what you're doing with it is much more important than what it is, IMHO. If I were stuck in traffic in an air-cooled Porsche, I'd like a 3.8 with street cams, bigger is better. At the very least, even if it were a 2.0, the T motors are great for exactly what they were made for - "T" for "Touring". My boss built a neat little motor, a 2.0 with 2.4 "T" CIS cams and high compression; this is the greatest little street motor with abundant torque at slow speeds....connected to a 8:31 915 gearbox it is a pussy cat in traffic and a sweet highway cruiser. The key is that it has working cylinder pressure at slow speeds, so it feels peppy, like a diesel. However, when you really give it the stick like a hotter 911, you realize it's not there in the same way. Different needs. He has plans to use it as his daily driver. Not the case for some of us...
If I were driving a narrow early 911 sportily, I'd keep it simple and build a roughly 2.7RS spec. It's a classic performer. A serious weapon widebody car, a bigger motor, a racy 3.4 or 3.6...why not. Stuck in a narrow vintage racing class running 2.8L and having trouble keeping up @8000 rpm, yes I'd max out a 2.8 SS on a 3.0 Turbo case and wind it to 9500 and rebuild it every other month..(not quite) all about application and taste.. If I was really racing and I
could, and the point is nothing else but to go faster (regardless of all else), I would turbocharge anything I drove. More power
However, there are other considerations. Street driving? What kind? With the wife? Track only? Limited by class rules? What about the sound? There are choices that are more 'aesthetic' or 'taste' oriented. Do what speaks to you. Try to try out some different combos if you can..
There is really no 'wrong' answer. You will enjoy yourself any which way you go. That is what this is all about. But there some answers that are much more right than others.
