^^As above, you don't want the Mi16x4 drivetrain if you're after lots of power, they won't take much more than they have in the 405 without serious work.
What kind of budget are you looking at - I know you say money is not a problem but you could spend anything from a couple of grand to 6 figure sums easily...
Do you want to run off the running gear from another road car or do you have enough to go bespoke as Pete mentions?
Bespoke isn't a problem, done a few of those
________________________________________- Bespoke rollcages/additions/adjustments. Half cages right up to complete custom spaceframes - MSA/FIA spec, CDS, ROPT, T45, etc - PM me
Custom-made polybushes available - need an odd size or fitment? - anything from batch work to one-off pieces.