When I did my sons head gasket I was very surprised to find plastic dowels as it is a 2003 build 2a, as far as I know the motor had never been touched (280,000) When I opened it up the dowels were non-existent, just bits of powdery plastic smeared around the corners of the block, I fitted the steel dowels that cam with the rebuild kit (no idea who's) have had zero issues since, nearly 80,000km now, so I would have no fear fitting them again.
cheers
Redd

