Engine bay differences z3 and 318

[1.9lz]

I have been looking at v8 conversions for 318's and most of their faq pages say not to use a z3. I have a 98 1.9l z3 and i dont really see that much of a difference b/t the engine bay of a 318 and z3, so my question is would one of these v8 conversions work on my z just the same at it does on the 318.
If I can do the engine swap in the z with relativly little extra work I would jump all over it. Thanks for any help I can get.