Other than insignia and color, how different is this one from its British equivalent? Yes, I'm thinking of Dr. Who again, and UNIT certainly wouldn't have gotten use of a Chieftain tank in the 1960's or 1970's, and would have been lucky to get something more antiquated.

The most important difference is the lack of bazooka plates. It also has the metal 20 pounder gun with mid fume extractor. Everything should be there for a Mk 5 with added glacis front armor. It has the later Mk 3 turret with the forward mounted loader periscope. The new Korean War Mk 3 has the earlier turret and bazooka plates. It also has the earlier 20 pounder gun without mid barrel fume extractor.
Grant

Much more than that were changed and it depends on what year you are depicting as to what needs doing. Many small and large changes over time and most important is the rear fuel tank...
Get this book:

If you can find a copy (Now out of print)

Do a search of the net:
http://www.ammssydney.com/australian-centurions-in-a-nutshell/

http://www.ammssydney.com/centurion-mark-51-arn-169108-vietnam-modifications/

http://anzacsteel.hobbyvista.com/Armoured%20Vehicles/centurionph_1.htm

https://www.youtube.com/watch?v=oIEMKiwxSsE

and you will get loads of data.

The Australian kit still provides much that you can use for a British Centurion. AFV Club hasn't made a Mk7 kit with the extended rear hull and pagoda air louvers.
The Australian kit lacks Sprue K, the bazooka plates and Sprue R, rubber gaskets? and a circular part that looks like glass for the copula, and the metal 105mm gun. Otherwise it has the same sprues.

Look at this thread for a BAOR Centurion, but it mainly talks about the replacement using the 105mm gun.
https://armorama.kitmaker.net/forums/260240&page=1

The 20 pounder gun was used for training until ammunition stocks ran out.
It wasd a simple task to switch barrels, according to Dunstan.

Grant

I just cannot imagine Tegan Jovanka driving one of those things!

I suppose I should ask what actual color the tank is supposed to be? The kit directions are quite useless for that.

Look for the Centurion used in the movie Help.
It seems to be an OP rather than RTR tank. This link might not still work.
Never-Before-Seen Photos of The Beatles from Eight Arms to Hold You.htm

Some quotes;
The budget was quite large and Lester splurged on splashy sequences like the final scene on Salisbury Plain co-starring the Third Division of the British Army’s Royal Artillery along with a number of their Centurion tanks
And this comment;
https://www.beatlesbible.com/1965/05/04/filming-help-49/
Richard J MartinAOL
SUNDAY 27 DECEMBER 2015
When the Beatles came to Salisbury Plains to make the film help. They were allowed to make use of my Self-Propelled Guns. I would get my Soldiers up at 4 AM in order to get the SpS to the Beatles. The Beatles never said thank you to my Soldiers for getting up that early. I was pissed with the Beatles and they knew it. Retired RSM Royal Regiment of Artillery

This is what markings and info I could glean from the tank in the movie. The number is 01ZR63, the red/yellow square number is 38, there is a yellow circle with three black triangles forming a triangle on the lower left glacis plate and a black triangle under the right side turret stowage boxes. One other tank in the background had a triangular plate with some sort of sign on the rear turret. The main tank is a Mk 5 with the early turret with the original loaders periscope (not on the front slope of the turret) It also has the earlier version of the 20 pounder gun w/o the fume extractor. This may not be the same tank, but in the tank that blew up,the rear fuel tank is not fitted and there are some small black boxes on the rear hull, probably associated with the controlling the pyrotechnics when the tank blew up.

On color, look at this thread; Bronze green and black.
http://armorama.com/forums/200832&page=1&ord=1

Grant

I did see the "Help!" movie years ago, thanks for the heads up.

BTW I thought Australia used a different color than the British.

The Cents (Aust) were supplied in Glossy Bronze green and carried that colour for a few years. By Vietnam the new Lustreless OD was in effect and the tanks were painted in that for the rest of their service during the 60's and 70's when the Leopard AS1 replaced them. Lustreless OD is a hard colour to match and varies tremendously even out of the can (we painted five tracks from the same source and got three distinct shades). The old go to Was the Humbrol French Artillery green (179 was its last release number). I like Faded OD from Testors Enamel but getting hard to find. Another option is FS 34102 lightened with 20% white and matted down with flat clear or dullcote. There are also specific LOD paints from Mousehouse (Very good) and others. Some Cents in Vietnam got spare bins and other parts from British and Kiwi stock still in the Deep Bronze Green and were seen like that in SVN.
Al