Exhaust Manifold I.D Help, Please

[Casey]

Does anyone know which kit are these from? White plastic underneath the chrome plating:

 

[Mark]

AMT '66 Impala

[Casey]

44 minutes ago, Mark said:

AMT '66 Impala

Thanks, Mark. The LH exhaust manifold shown on the instruction sheet in the Gen Disc topic looked a bit bunched together at the lower end compared to the instruction sheet's drawing, so I thought they might be from something else.

[Force]

I would say AMT 66 Impala too, they are model replicas of the 1963 Mk II 427 "Mystery Engine" cast iron headers.
The Mystery Engine was the predecessor to the 1965-forward Mk IV Big Block 396-427-454 Rat engine but doesn't share much with it's younger brother other than similar outside appearence, the mystery engine has more in common with the Mk I 348-409.

[Mark]

In the thread about big-block Chevy engines, the Impala came up as (probably) the first kit that had one.  I mentioned too, the Impala engine was transplanted into the AMT '61 Ranchero kit later on.  If you have a first issue V8 Ranchero kit (from 1977) or see one on eBay, check the box art.  The side panel shows the engine with these manifolds (though the V8 Ranchero kits always used the stock ones from the Impala).