Hi Gabe,
If you need some inspiration for the eventual amazing outcome of shoehorning a watercooled engine into an air cooled chassis, I just came across a really insane build, a 964 with a GT3 engine and a bunch of other amazing upgrades, they call it the 964 RS GT. I would think that you already know about it but didn't see you mention REEN Automotive so not sure?
There are some cool videos on Youtube and a detailed interview with the founder Philip Hoffmann on the Car Chat podcast. While the 964 chassis is somewhat different, the rear mounting area should be the same, so maybe their engine crossbar works? You could also try and find out what they are using for front radiators, if you haven't gotten the CSF ones yet.
Cheers,
Lukas
https://reencars.com/rsgt/