I think this is a great idea. I suspect you'll need to find another way to hang the coils and wires to keep them out of the wet.

It would be interesting to get some dimensions to compare this motor size-wise to the Ford modular 4.6 which does have some tight-fit issues at the heads so you can determine potential fit issues. Of course constructing custom headers to fit around driveshafts, suspension etc will be some work, as will the transaxle fit/adapter/driveshafts. Sure looks like a cool "alternative" option for power.
I believe a guy in Sweden stuffed a BMW V8 into a Pantera with very nice results (and awesome sound). Also, since some early DeTomaso Guaras were shipped with a 4.0 V8 BMW powerplant nobody should be flaming this concept at all.
Can I get a ride when you're done?

Mark