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These eBay manifolds have the casting number D1ZX-9425-DA on them. That number is the casting number of the original Ford standard height aluminum manifold. Something I've never seen on the Blue Thunder manifold before, and I'm not sure what to make of it.
The hi rise manifolds we refer to as the Blue Thunder manifold never had that casting number on them. And they were raised in comparison to the original D1ZX-9425-DA manifold.
The original D1ZX-9425-DA manifold didn't perform any better than the factory iron manifold, they were both standard height manifolds.
Can't tell if Blue Thunder has simply added the casting number to the same hi rise manifold they've been reproducing since the 80s. Or if they have recently begun reproducing the factory standard height aluminum manifold. That may mean they now offer a standard height manifold, and a hi rise manifold?
Have I confused you yet?
-G