I reckon the standard turbo should be good for over 300bhp with the nice rs500 cooler.
Current plans are laid out like this:
December : Get sierra running with 310bhp or so and do paperwork to get on the road in jan.
Jan: Get rwd nova up and running with 250bhp + 100bhp nitrous.
Feb: Get sierra up to 340bhp + 125bhp nitrous (will yield around 450bhp as nitrous doenst give as good results on a cossie as its jetted to according to Rod)
July: Get mini running with 270bhp + 75bhp nitrous
August: Pull engine out rwd nova and put back in with arrow rods, 270bhp + 150bhp nitrous
Next winter: Put 350bhp + 150bhp nitrous engine in mini