what do a12 GX engines have that a regular a12 doesnt? gx carbs and exhaust manifold?

A12GX engine includes these differences from single-carb A12 engine:
* Camshaft
* Water inlet pipe
* Pistons
* Head gasket
* Cylinder head
* Intake system (manifold, carburetors, air cleaner)
* Exhaust system (manifold and exhaust pipe)
* Rocker cover
* Distributor
* Choke cable
* Breather hoses
* Water hoses

I think a period correct, restored and complete A12GX engine would fetch a good price. Been many years since I have seen a complete A12GX engine in Aus, one that isn't a mix and match unit.

I paid for a complete A13 with an automatic 3 sp transmission out of a wrecked 1974 b210 $ 140.00 complete with low miles like 4 years ago from Ebay in the US.