SWB manufactoring sells an engine mount, although it isn't cheap, it already has 2.5 degrees built in and helps you align the 4 mounting holes with the left shift of the engine due to the offset. Check them out, could save you some time, it did for me.

And I also just made the engine box sides the same length and used 4 standoffs from Aerografix's all cut to same length, no offset.