Thanks Chris
I understand where you’re coming from. My feeling is that they wouldn’t cause a problem, although I am happy to be disabused! I don’t see any problem with the exhaust manifold or engine mounts (obviously steel) or with certain bolt on bits such as the inlet manifold and carburettors. Anything with Allen bolts I would not change.
This is a very interesting website in respect of flange bolts.
https://www.fbabolt.com.au/flange-bolt-tech.html