There are so many different boxes, some may or may not have same bolt patterns. Although obviously the ZF has a torque converter.

I'm sure some of the companies, PMC, HPR, Domiworks etc would be able to produce a kit for a YB. Not sure in general how popular it would be. But they're all producing more and more kits all the time

Either way, DCT or 8HP, both great options.

I did consider them myself, but just not convinced either would be strong enough, and it could turn into a very expensive gamble to find they break. Either of them are not easily upgraded.