Step 1: Dump that Old Bumper!
First, locate all bolts affixing the bumper to the frame. Soak those suckers in PB/WD-40. Wait 10 minutes...and soak them again.
Unbolt everything, and drop the old bumper away. Take your time....those bolts are probably large, and you probably can't break them off, unless you're sporting 26" arms, and a 'born to kill' tatoo.
As for your old bumper, I'd suggest storing it, in case this project goes wrong, OR just in case you decide to sell the truck later, and fear your new custom dragon tooth bumper isn't going to be a 'good selling point. If you have plastic trim/moulding/etc surrounding your bumper, be careful removing those...you may need them later, and just jerking them off is sure to crack them...take your time.