The plenum needs to be on the intake manifold.
Every once in awhile a one-off intake manifold with a large plenum shows up on EBay.
Here's One.
Although, I've seen better.

Then theres the Ford Racing manifold.

Frank McCoy aka Mod-deth aka Mid Life Crisis aka SVT Doood aka mcgainer is a SCAM ARTIST Pre98 Zetec - Some Mods