Hello Mike.
Your request doesn't sound too good. Has Bravo Zulu's engine given up for good? I used to own that aircraft and sincerely wish I could help you but I have no contacts to assist in your search for an engine or a mount. It would be great with a Rotax up front, it's a superb aircraft. I had problems during my ownership with the engine and getting my hands on parts from Austria was not an easy task.
I know a superb welder who would make you a frame from diagrams for a Rotax installation I'm sure. He repaired my frame on an RV4 to a very high standard.
If you supplied the steel 4130 I think it is with the diagram he may be able to help you.
The number I have for him is 07734 232994, his name is Dewi, pronounced Dowie from Oswestry Shropshire. He welds for Linstrand balloons.
Good luck with your modification and I would love to see BZ flying soon
Regards
Paul Lewis