I need the plenum structure under the vent cover that holds the wiper pivots. Anyone make that?

Pics would be helpful to identify the exact part your referring to.

check CarPartsManual.com 

See pic

So it looks from your photo, that you need all of the sheet metal under the cowl.

Wow I thought I have seen it all

Use this to figure out which wrecking yard cars to chop up.

http://www.carpartsmanual.com/datsun/Z-1969-1978/body-240z/cowl-top-grille

7 minutes ago, Zed Head said:

Use this to figure out which wrecking yard cars to chop up.

http://www.carpartsmanual.com/datsun/Z-1969-1978/body-240z/cowl-top-grille

Didn't the OP say 280Z? http://www.carpartsmanual.com/datsun/Z-1969-1978/body-260z-280z/2-seater/cowl-top-grille

Either way, it's just something that would have to be cut out of another car.

1 hour ago, SteveJ said:

Didn't the OP say 280Z? http://www.carpartsmanual.com/datsun/Z-1969-1978/body-260z-280z/2-seater/cowl-top-grille

I didn't narrow it down, just found the part shown and posted a starting point.  But, since you brought it up...

http://www.carpartsmanual.com/datsun/Z-1969-1978/body-260z-280z/2-seater/cowl-top-grille

Found a web site.  Who knows?  436 Euros for the top piece.

http://www.autospares.eu/search.html?search=search&article=66300-N4700&term=0&sort___search_results_by=final_price&chk_smode=on&smode=A

 

http://www.autospares.eu/price-lists/nissan/2568/

Finding good donor cars that aren’t also rusted in the cowl area will be hard to find. Most of that got cut away when the road racers were building true tube frame GT2 cars for SCCA racing. I bet most of it was discarded.

Some of the inner structure can be hand fabricated.
 

Looks like the firewall is rusty too.

Isn’t someone reproducing the firewall panels?

Edited August 30, 20215 yr by Racer X

4 hours ago, Racer X said:

Most of that got cut away when the road racers were building true tube frame GT2 cars for SCCA racing.

It's a 75 280Z.  I wonder if the rest of the car is similar.  That is not a typical rust area, to that degree.

Might be best off to find a new shell and move all of the good parts over.

https://www.classiczcars.com/profile/35466-ennisdavis/