1999silverado

Hi im George and i have a 1999 Silverado with a 4.8l 5speed manual (nv3500) and its 4wd (not sure of the t case) and i would like to build my engine to around 450 ft lbs but the nv3500 cant hold that much power. I was wondering if anyone had any cheap suggestions for transmission (manual) and t case if i need a new one. And suggestions on what to do to my engine to get it where i want it. Thanks