That's the problem- - - -it won't work better. The leverage of the large radius of the big wheels and tires and the inertia of the weight of the truck will make that puny little disc brake far less effective than the original drum system. You'll need a disc 3-4 inches larger in diameter, and a caliper with much more swept area just to break even- - - -or maybe a 3000 PSI hydraulic system to apply pressure to the existing caliper. Then the pads will wear out about once a month. The laws of physics are not "suggestions".
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!