Body panels how comes?

[raseeda green]

Hi all
Can any one explain which sills and arches fit the best! Or does it matter which ones?

I have been on the search for rear wheel arches and sills, so it's come to my knowledge that there are a few different types of these, so does anyone in the game know if there's ones that fit the best or do they all do the job? And if so where is the best place to get these please?

Cheers
Lee