If you have stock S heads and webers you have 35mm intake manifold. 75 and later S had cis which you can plug and the heads are 35 in and 35 exhaust. these heads have worked great for me with the 67 S manifold 9.5 cr piston 40 webers solex on 75 S case. Have not missed 66 mm crank. I wonder how much better 75 S heads are than 2.0 if you get 9.5 or so compression. Be sure you don't get 74 heads as they are small 32/32 like the Ts

2.7 heads sounds incorrect. he is going with 2.2 barrels. they also have the funky cis relief. 2.2-2.4 heads ported to match your manifolds seem like the best idea.Am I missing something?