Physical difference in crank carriers from 2.5 to 2.7?

[78F350]

If you want a definitive answer, try contacting Jake Raby. https://flat6innovations.com/
Here's a post about mixing various M96 engines that I read a while back. Not an answer to your question, but similar topic:
https://rennlist.com/forums/996-forum/684465-is-there-a-diference-between-a-3-2-986-and-3-4-996-head.html#post9339329

I carry out this type of interchange frequently. I have included an interchange table in my assembly manual that should answer most questions.

Combustion chamber variances of 3cc are the biggest difference in the two heads as long as both are from the same era. Both engines must be "5 chain" to allow this to happen easily. There were no 3 chain 3.4 engines, and all were 5 chain. The 3.2 heads will increase the compression ratio of the engine due to their smaller chambers. The 3.2 and 3.4 share the exact same camshafts and the only difference between the 2 internally is the bore size, CR and intake arrangement.

It is possible to install 3 chain heads on a 5 chain engine and 5 cain heads on a 3 chain engine, according to what the combo is you are shooting for.. Hell, I have even used a 2.5 Boxster crank inside a 3.8 liter 997 crankcase for a short stroke, Big Bore HI RPM beast.
3.6 heads have vane cell adjusters for their vario cam + cam arrangement and NONE of these parts are interchangeable with the earlier engines to include the camshafts.

Its all in the combo.