I suspect that if you spent the equivalent amount of money that you would need to purchase a brand new Gould Chassis plus sequential box and NME V8 then you may well be able to match the current performances - that is if you also had the talent of either Martin Groves or Scott Moran.
How about the 3 Litre Cosworth TJ V10 (which will have 900bhp and will run for 1200km between rebuilds) slotted into a Predator?
I think Paul Ranson hit the nail on the head with the comment 'If you were looking to build a car to be competitive in the championship would you ever choose a bike engine?' I suspect the answer would be NO assuming it was a money no object design.