Don't think there is such a thing. I am pretty sure the 454 actually got a fuel injection set-up like the marine 350 or any other gen III engine. They have fuel rails with injectors not buried in the intake plenum.
Keep looking on Ebay for Mercruiser EFI Marine Intake. They are usually lots to choose from.
Installation will be very similar to my Mercruiser/GM MArine intake installation.
You could also simply find a Vortec 454 intake manifold. The 1996+ Vortec 7.4L 454cid uses 24 pph injectors which are replaceable by larger injectors UNLIKE the smallblock Vortec intake manifold which you are stuck with the 19pph poppet fuel injection spider setup. On the Vortec 454 setup the injectors are in between the upper and lower intake plenums just like the Ramjet 502cid/510 hp and teh all aluminum ZL1 454cid/495 hp intake. Here is a pic of the Ramjet ZL1 intake and engine as installed in a 1969 Camaro. There were only 200 Ramjet ZL1's built. They even used teh old Winters foundry tooling with some minor updates dpne to teh old molds.
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