The simplest way is to take out the stock bumper, remove the plastic crap from the structure, and weld the external steel bumper to the bumper structure. This way, you will not need to fabricate the frame mounts - the stock attachments are pretty strong.

This is how the custom fabrication shop did the steel bumper for my Rodeo. The whole thing took just half a day.

Oleg
Axiom 4WD 2004: OME shocks, 32" BFG Mudders, RockSliderz, OME929+2" spacers, Stinkyfab bent RE rear links, front ARB locker, rear No-Slip locker, DOR front axle lowering kit, custom middle section skid plate, IronMan torsion bars.
Deceased Rodeo'02 4WD.