I noticed these are specifically for the magnum engine, do you think there would be a cooling issue because the ports are smaller? I have a set of steel shims that are like this and wasnt sure they would work.
Steel is not recommended for aluminum surfaces so if you have aluminum heads or intake don't use those.
The Felpro gaskets work really well for intakes.
On the 1121g the surfaces better be straight, but otherwise you should be fine.