I have been wanting to do the same scoop on my early 79 series hood (same). I believe the Fiberglass Factory in AU makes both the scoop and the hood with the 79 series intercooler scoop built in. I have a topmount cooler, but it has a dorky hood scoop.
Frp.com.au sells the hood scoop hood and all sorts of FRP stuff for cruisers. All I know is strayans put bonnet scoops on everything. Too right.