rods and pistons

is there a way to change out the rods and pistons without having to pull the engine? I was thinking of maybe just taking the heads off and the oil pan off, but could i get them out that way?

You can't even get the pan off completely without removing the engine in our trucks... That said, you'd want it out anyway on a stand, especially when honing the bores and having to measure each bore for warping. Also it makes life easier when you can roll the engine over and pull the crank without fighting it. (Same goes for installation)