ive seen a wire wheel do amazing stuff to some really ****ty/corroded stuff. unless its so corroded that the integrity of the piece is questionable (such as holes or deep pitting). i really doubt you could find anything at a junkyard in much better condition than yours.
yours a lot differentthan mine and i cant really tell from the pics, but how hard would it be to fab a piece from scratch? maybe some diamond plate, or something else if thats not your taste.

 

looks like it wouldnt be difficult to mock sumthing up, as the center piece appears flat with only 4 holes for bolts.

BUT if underneath this piece,theres some function that i dont know about and it has other uses than just display/ protection, then disregard my above statement.

 

Alright, help is here with your "running" problem. No matter what a paint says about it sticking to plastic you must always prep first! And by prep I mean more than clean it. You HAVE to scuff the surface. Especially since those engine covers are treated for stuff NOT to stick to them (like enging gunk) Just take some 150-300 grit sand paper and go over it lightly. Just hazing it really. Then clean it with a prepping cleaner, or rubbing alcohol works awesome! If you're doing metal, use mineral spirits. Then primer!!!!! PRIMER PRIMER PRIMER!!!!!

After that, lighter coats are better coats!

Some other information: I worked at Home Depot as the Paint Department Supervisor and a) Krylon Fusion blows b) It can't be mixed to custom colors c) You would have an easier time using a model paint as you can get those in thousands of colors, including metallics, and most are car color coded already. And those are meant to stick to plastic, but you STILL primer. I know its a kids hobby but I still put models together and you HAVE to primer. Its the not so well known must-have step.

P.S. Don't use fusion! Get a touch up paint that's close, your car looks to be close in color to the Saturn color called Champagne, but just browse your local car parts store that sells auto paints.