I dunno, I really appreciate these sorts of threads as the information (and, particularly, the observations) shared get me thinking about what parts to collect for "next time." And none more than revisiting Conklin's old article, which is excellent but for some heavy handed edits. He selected the 2.5 as his "winner," but went on to build the 2.8 iirc? And I can see why, given his observations…

Time with my "2.2E+" tells me I could live with it as is and just keep driving it for another 20-30 years if that's my lot. If I was willing to flare my car, and add a 915, the 2.8 sounds pretty appealing—but time spent with other early 911 engines and comments in this thread as well as Conklin's superb article suggest the ideal setup, for me, might be a 2.2S with short gears. And, if budget permits, with MFI or EFI and everything built to rev to 8000 rpm. I'm far more interested in a bright/keen engine that sings up top than one that makes good torque down low. My car isn't an around-town driver, and I don't have or want the tires for big torque.