I'm not aware of any direct fits for the Raven magazine well, apart from Triple K and factory mags. There is a seller on Gunbroker with extended 15 round magazines for the Raven, these look like a copy of the old Triple K "hi-caps" and the one I own functions pretty well. Apart from that though, I'm not certain a Beretta mag will fit and feed into a Raven.Will a Beretta extended clip fit in a raven .25 auto hand gun?
Are there barrel modifications and what website bests go with these purchases
As far as barrel modifications, I'm not at all sure what you mean. The Raven barrel is cast into the frame and isn't readily altered in any meaningful way, without some machine tools I suppose. As far as pieces-parts, eBay, Gunbroker, etc, are your best bet because all variants of the Raven have been out of production since around 1994, so what's on the market is generally used parts and the occasional new old stock items that show up.