I have my father's Winchester Model 1894 25-35 WCF SN: 228366, what year was it manufactured?

Can you tell me the year this rifle was built and where to buy ammunition?

I think the year of manufacture for serial number 228366 is 1901. I just when to this site- http://www.armscollectors.com/sn/windates.htm
as for the ammo I think you have to special order it?

25-35 WCF ammo is available, try Cabelas, Cheaper Than Dirt, Sportsmans Guide, etc for online ordering or local sporting goods stores that sell Winchester ammo may have it or can order it for you. You can just type 25-35 WCF in a search engine and a lot will turn up. I see it at my local stores regularly. This is a great round for hunting, just got lost in the flurry of new guns at the turn of the century. Winchester has started making guns with the same cartridge to feed the nostalgia for old guns. Before shooting (and buying a bunch of bullets at todays prices), you may want to have a gunsmith take a good look at it just from a safety standpoint as well as preserving the value if there is something wrong. In general these were very durable guns which is why the Model 1894 is so popular. I hunt every year with a Model 1895, heavy to carry but it's a goody.

your gun was manufactured in 1901