Need your advise on my idea for an engine swap before I potentially open one big can of worms

I'm starting my next project, it's a 1610 with a oil leaking, rough running twin Briggs. I have a good twin Kohler in a 1720. Will it fit without much modification? I'm not afraid of somethings needing to be done, but before I pull the Kohler and go through the work of cleaning and painting and it won't fit, well you know the rest of the story.
Just wondering if someone would know the answer to my question.
Thanks