fixing up 1991 f150 with 4.9 6 cyl the brackets on motor for all the accessories are made of aluminium or magnesium is there any coating or paint i can use to make them look better on newly painted motor. i would like to clean metal in some manner or paint them silver but what can i use on such a metal? any suggestions

 

Use any paint you choose on the aluminum… they aren't magnesium.

 

As Krooser said, the brackets are aluminum. You can use a degreaser to help break down any grim on them and then wash them down with water and dry them.
You can then hit the whole thing with a small wire brush on a drill, like this one:

Then wash and dry again.
After that you can spray a coat or two (or until fully covered) with some aluminum colored paint. You could also clear coat if you so wish.

This is mine before:

And after:

 

I used an aluminum-colored rattle-can paint (forget the brand, but it was probably Rustoleum, which I usually use) on the "alternator/air pump tree," and it came out well.

 

Eastwood has some VERY GOOD engine detail paints

Here is one such example I always keep on hand
Underhood Detailing Kit
1st had experience

 

I used air conditioning coil cleaner to clean off my aluminum parts. Soak it really good and you see it start to foam up. Rinse off and dry, repeat if necessary then used clear coat paint(high temp) to keep them from "frosting" up with that white oxide aluminum does. Looks good years later.