Jeep Repair Problems? Ask a Mechanic for Answers ASAP
Hello and welcome to just answer Jeep. Advance Adaptors have exactly what you are looking for. They make a kit that you can purchase to put your Chevy engine into your YJ. As far as the 700R4, I think you should be able to make that work also. Check wit the people at Advance.
Click on this link, it will take you to their YJ adaptor kit page.
Hope this information helps. Let me know if you need more assistance with this.