Thankyou very much for the info - I expected a few yanks to be running the system, maybe some A body's would be as close as I'd get, but an Aus Charger is on the money! Cant get more specific than that!!
Got an Email from Calvert racing today saying they can help me out with the odd spring length ( I guess they'll tell me to drill the rear section like you just did!) so I'll call them tonight our time and place an order.
Good luck with power additions in the future!
PS - got a pic of the car???