Update
Well, I was in town last night to pick up a few things and was in the local farm and home supply. They are a sort of big box Stihl dealer. They sell lots of them, but don't really know anything if you need help. Anyway, as I walked past the chain saw equipment, I stopped to see if I could find a 63PMC-62 chain for the CS-400. I didn't see any hanging there, all were PMC3. The guy working there asked me if I needed any help, so I asked about the chain. He said that Stihl doesn't make the PMC, non safety chain. PMC3 is all they make. Needless to say, I didn't ask any more questions. I could probably get better chainsaw information at Walmart. While I was standing there, I looked down and saw a lone GB bar lying there with a price written in black marker ($22.99). I didn't have any idea how they would have gotten this. They do not sell GB at all. Upon closer inspection, it was 18" 3/8 low profile bar with mounting hole and slot that looks just like Oregon A041. It also has the large radius sprocket nose and is solid, not laminated. Neadless to say, I bought it. It rang up as special order parts. Haven't been to my dad's place yet to try it on for size, but I think it should fit. Part number on the bar is POX18-50SH. I couldn't find fit information for this bar online, but I am hopeful. The Lord certainly works in mysterious ways!