I have used patch panels from several sources. The inner cowls I got from Chevy Duty did not fit at the bottom front where they connect to the floor but with a little hammer work and a small splice panel it works fine. If you expect these panels to fit exact then you will be disappointed. Most will take a bit of custom fitting to make to work. When they do fit just right you should enjoy it but also take a minute to look again as you might have it in wrong.

As for your inner corners, they make two heights. The full height are for full replacements while the 4 inchers are for splicing into what is left of your old inner corners.

The inner to outer cowl panel I got for the right side had to be cut in half, reshaped and rewelded to make it work.

Good luck and have patience.