The Cobra outdrive is a derivative of the Volvo-Penta corporation and I believe there were and may still be some diesel pairings. I don't think I've ever heard of a Detroit/outdrive set up but, like my pappy used to tell me...."boy! we could make up a whole new world outa just what you don't know!" so, there may be some.
At any rate, where there's a will there's a way and a determined fellow should be able to make it happen. After all, the Detroit is just another engine.
Some problems that could arise do come to mind:
The 5.7L GM platform as well as the 7.4L has ready made, off the shelf hardware for doing what you propose while it might be a reach to find coupling hardware for the Detroit.
Additionally, there may be quite a weight difference between the diesel and the gas engine. I don't know offhand what either one weighs but I believe the Detroit will put your stern much further down in the water than the Chevy will.
Then there is the shifting. The Cobra system briefly shuts the gas engine down when selecting forward or reverse so that the drive isn't damaged. I'm not sure how this would work with the Detroit.
I'm sure there are others that know way more than me about this stuff so maybe you'll get some other offerings to help you decide. Good luck.