I see the problem Mark but there is a solution with the Toyota V8. The differential, when the oil pan is properly made will sit on the side if the engine. The oil pan flange is narrow, much more narrow than the V6 cologne. Whats more important there is no offset present in the V6.

Take a look here, here and here.

Aluminium heads would be sweet, thats a big weight gain and a lot to offer in handling.

Will you be using a custom made flywheel ? Judging by the flange yes.