The best I could come up with after much research, is to use a 20 gauge wire for the entire length of the red fusible link wire in the diagram, and put a 40 amp Maxi Fuse in it. Any comments or input?
Yes: That's wrong. A 20ga wire will burn up quickly; before it does that it'll cause severe voltage drop and nothing electrical in the car that draws more than a couple of watts will work well, if at all. Don't know where you got the idea a 20ga wire is needed. If you are replacing a fuselink with a fuse, you pick a fuse holder that has the same gauge wire as the rest of the line you're putting it in.
Also not sure how you wound up picking a 40A rating for your fuse.
(Me, I would vote for putting in the correct fuselink.)