the steering box and collumn will interchange as will the engine and transmission. Everything else will likely be a wasted effort. Although the 3/4 ton springs, axles, and brakes are practically bulletproof, they are not much of an upgrade for a 1/2 ton truck. The 3/4 ton gears are typically 4.56:1 which will likely reduce the cruising speed of your 1/2 ton. It is also much easier to retrofit a 1/2 tons brakes to disc. There isn't much aftermarket support for the 3/4 ton drivelines.
