New shells for my VR6? Where from and how much?

[McPikie 3]

Guys, my VR has developed a little knock under load. It may be doing it all the time, but I can only hear it under load whilst driving.

Basically, it sounds like either piston slap, or the shells have gone.

Obviously, I need to whip the sump off and check them. Can they be done in situ, or is it time to take the engine out?

Also, are they a VW only part? Do they make oversize ones too??

HALP