How to change player's body (package, scale)?

So what I want to do is make a script that changes one player's body when the game starts. I want it to change to the normal body scale and 1.0 package, but I can't find a good way to do this. I've tried welding body parts to the character, but depending on what package they're wearing, it messes up. I've also tried deleting the player's body parts, then putting the new ones in, and then using MakeJoints(), but nothing seems to work. I would appreciate help if anyone knows how