Just select your self sim in bodyshop or CAS (or even in game) and give him SBB clothes. Cause it is basically just a change of clothes, no beheading required.

If you want a showerproof skintone that lets your sim keep his muscular form in naked state (shower), you need to give him that skintone before you start playing with him.
I take it you already have the meshes and clothes and skintones you need? If not, there's plenty to be found right here on insimenator.net.

Happy simming.