Get Fort. Saves to Run Off INT?

[[CLASSIFIED]]

I have seen the "X stat to Y bonus" thread, but other than seven levels of Nightcloak, it didn't list a way to either gain INT as a bonus to, or replace CON as the main ability for Fort. saves. Therefore I ask– is there a way to get Fort. saves to run off INT?

Preferably, this effect would be permanent and non-dispellable.

[FMArthur]

You can add it as a competence bonus twice/encounter off of a 1-level Factotum dip. Or you can take the feat Martial Study (Mind over Body) and replace it with a concentration check once/encounter, which you should have as a good value anyway (but you would only have the Initiator Level to take the feat after 10th level). Really you should just try to have a good Con modifier though.