People convert the API 325 circuit to a 312 pretty often. Going the other way like you want to is less common but isn't hard. There is more going on than just the transformers, and those little details do matter. Changes to passive components on the inputs and outputs that may be easy to make, or may require some physical creativity depending on the boards you are using. I don't know the CAPI boards well enough to know which it'll be for you.
But there are oodles of posts on this subject over the years all throughout the archives. I'd suggest starting there if you haven't as this one has been covered so many times that you probably won't get tons of folks eagerly jumping in to help without specific questions being posed.
Good luck! The answers are all there and the schematics are very straightforward.