got 2 duramax badges and thinking of putting one on the tailgate but dont know where.

under handel

If your truck is your avatar photo, you probably have the Powerdome hood (looks like it). I'd put them there on the rise close to the windshield.

I second the under the the tailgate handle that would look cool. I know a bunch of guys around here who take another and put it on the passenger dash, right on the air bag panel and it looks pretty cool.

I have a custom badge on my tailgate, right hand side. My room mate, Rydnhi4x4 has custom badges on his hood, which look great...Check out his garage.

Can you say "custom bow tie" :D

how bout on your forehead

Well, I'd put the license plate in the license plate frame and mount it on the front bumper.

Seriously though, put the D-Max badges on the hood on the sides of the big "scoop"-I guess that's what you'd call it.

I put mine up on the sides of my hood when I removed them to put my company signs on the truck.

On the sides of the hood.

I've got an 06' Sierra and the door badges are the ones that say Allison Transmission and then just DURAMAX on the right side of them. I bought a set off of ebay that have DURAMAX DIESEL on them (05' and older style) and put one of them on the right side of the tailgate, centered right above the GMC logo. I couldn't stand that I finally bought a Diesel and it didn't say diesel on it anywhere!!!!