I was told by Victorian RTA that I was allowed to go 20% bigger capacity which means only the 1200 is legal, but that was going back about 4 years. I still think you can get more than enough power with the right mods on A12. Admittedly there is no substitute for cubes!

When push comes to shove you put an A14 crank in your early A12
 
just machine counterweights a tad to fit the A12 block, rebalance assembly
bore for 76mm stock A15 slugs with tops milled to 29mm, A12 rods bushed
to suit larger pins, H89 oval port head and presto!

You get torquier engine than A14 and almost A15 due to rod stroke ratio
going down to 1.58 which increases gas speeds throughout the lower
and midrange and compensate at higher rpm with higher compression.
The oval port heads usually come on later in the rev range on the
1.72 stock rod ratio A14 but not this one it rocks all the way so this
combo is excellent for the street a real stump puller in any gear.