Sarco is probably about the best place around for FN-49 parts right now. Currently, they have brand new 8x57 barrels for $80.
http://e-sarcoinc.com/fn49.aspx
Also, check to see if your rifle has the older one-piece or the newer two-piece firing pin. If you've got the one-piece, I'd highly recommend replacing it with a two piece one. The reason is that the one-piece pins are somewhat prone to breakage and can cause slamfires when they do. Having an FN-49 go full-auto unexpectedly is not my idea of a good time. Numrich has two-piece pins.
http://www.gunpartscorp.com/catalog/...450&catid=2154
http://www.gunpartscorp.com/catalog/...460&catid=2154
Both Sarco and Numrich have 30-06 stocks, but I don't know what (if anything) would be required to make them fit an 8mm.