I don't think you want to. I have 4v's and 2v's and love them both but bottom line the 2v is the better head below 5000 rpm for street use.
My Edelbrock Torker for the 4v heads is MUCH smaller than the 4V port. There is a freakish difference. It's meant to be this way due to the huge 4V ports. I would love to stick the 4V torker on my 2v motor!
A local shop uses 4V heads, and a Yates intake gasket that is in between the 2v and 4v size and fills the port with epoxy and makes the ports smaller, and more efficient. They also use a flow bench to make sure it is done properly and flows equally and flows well.
Look @ the port plates made by MPG , they make that 4v port smaller and more efficient .I would stick with the Aussie head as is and look for gains in the Intake exhaust and camshaft design.
My 4V motor is on a drag car that see's a max rpm of 7000.Big 3200 conveter and 5.14 gears too.