Tunnel ram or no tunnel ram...

This is Indy tunnel ram without cover after initial cleaning. I was thinking about spacer under top cover but this is for future experiments. No room for anything in current setup.
I was asking about filling that void based on this plenum design.

View attachment 1716181643

View attachment 1716181644
Looks similar to mine that I ported.

IMAG1492 (002).jpg