Don't know much about the truck grill but if it's similar to the 33 (cast alum) then polish it if it's a driver. The nose of the car (truck) is going to see road debris and if it's coated with paint or powder coat it will chip and the alum will show through. And all those small slender fins will be a real problem to fix.

I polished the grill shell on my 33HR but left the finish between mirror & scotchbrite, not so shinny that it's hard to re-polish but shinny enough that it looks good and hides small scratches. And a few minutes with some medium fine alum polish will restore it.