Will my accessories such as my main crank pulley, water pump w/ pulley, alternator and its bracket ,power steering pump and its bracket, my belt that goes on the front, my idler and tensioner pulleys

Will those all transfer over fro ma 03 4.3L v6 to a 02 4.8L V8?

 

Nope, non of them. 2 total different motors

 

are bolt patterns different?

 

when did or did they ever change?

 

The 4.3 V6 uses the same bolt patterns and accessories as the old Small blocks. The new, GenIII motors are a complete redesign and have totally different bolt patterns and accessories. The only bolt pattern the 2 motors have in common is the bell housing on the back of the motor and even it doesn't use one of the bolts. The GenIII motor came out in trucks in 99.