G'Day again John, Have a bit more Bushranger info for you.
The RAAF used 2 different types of minigun ammunition carriage. The earliest type was a large rectangular box like the US C model gunships had. It was mounted just aft of the pilot seats (looking at your photo of your kits in assembly the box on the RH side with your "weapons Cache" in it the lower RH corner the Grey box is what you'll want) I believe this config was used until midway through 9 SQN In Vietnam until they changed to the pyramid looking Hopper style boxes 2 per aircraft behind the pilots seats again.
The ammo feed I believe for the Vietnam just ran behind the Quarter door and to the gun I'm not 100% but I don't think it was until after vietnam they had the holes cut in quarter doors for the flexi feed. Same with skinning over the windows on the quarter door that was a reasonably late addition too I think.
For doorguns the M-60's from the M-113 kit look spot on just might need the folded bipod added if they don't have it. However in 1/72 that might be getting a little too picky it's up to the individual! The doorgunners also had a rack mounted to the aft bulkhead on each side holding 5 M18 smoke grenades you might like to include that too?
About the other only major gunship thing I can think of would be the inclusion of the gunsights. The best i could describe them would be they looke like a mustang or similar aircrafts gunsight but inverted and hanging from the top of the windscreen pretty much! Unlike the US aircraft which had a complex looking system with a handle and a series of long arms to control the hydraulics on the guns which the RAAF removed.
I hope that wasn't too confusing just trying to give you what I have off the top of my head. If there's anything else I can help with fire away
Cheers
Cairnsy