The simplest way to increase your stopping power without doing major surgery to the brake system would be to install an appropriate-sized Hydrovac unit. It's a simple conversion, and it provided adequate braking for these trucks back when they were really used as trucks- - - -fully loaded, or more likely, overloaded on a daily basis.
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!