Direct link to the GSG-522 to GSG-5 parts kit @ CDNN.
Although I think some of the changes made to create the GSG-522 were genuine improvements, there's no reason you couldn't mix and match parts.
In case you haven’t noticed, I’m a bit of a Glocker. I really can’t have nice things, so the basic black pistols work just fine for me.
I’ve also shot rimfire benchrest. I even managed to win a local match. My best score to date was shot with a completely rebuilt Ruger 10/22 with a KID trigger and barrel, although my Remington 40XRBR is more consistant.
I started shooting rimfire benchrest in 2004, I think. I got into action pistol competitions in 2006.