Hi fellow Daxer,

I cant answer your question about the plenum but i feel your pain struggling to fit stuff in the Rush engine bay so this might help. You can get rid of the distributor then the area around the throttle body with that plenum you're looking at will be much greater and the attached picture shows what i did.

Obviously, you could fit one of those camshaft triggers with that horrible pickup which ruins the look of the cam cover but this solution is neater and still means you can bin the dizzy.

how is the EFR performing?