Not totally sure what the best way would be to fix the cracks, but I know you can buy a new emblem for the grille. I bought one for my '75 awhile back. I got it from Cheyenne Pickup Parts, they have alot of odds and ends that are hard to come by. That grille you have is also very hard to come by, you can't buy the '75-'76 (or '73-'74s for that matter) grilles brand new anymore. The only new replacement stock grilles available now from what I can see is the '77-'79 and also the '80 model, and most of them don't even come with provision for an emblem.