99?-03' to a 04'+ silverado front end

what all do u need for the swap..fenders core support, grill/lights.....? do u need the hood also?

All you mentioned plus you have to get some new headlight brackets, yes on the hood and the bumper and brackets.

for the GMC all you need is; bumper brackets, new bumper, and grill. That's it. I did it on mine. Super easy. You do not need anything else. The hood, fenders, and core support all stay.