Any one looking for .351 ammo can find it at Coins Stamps and Guns behind Elwood Epps ,North of Orillia Ont ,on hwy 11.
50-300 usd
I heard a few rifles from 1917 and 1915 that sold for about $1,000
from 1907 through 1957 only 58,000+ were made, in fair condition it should fetch 500.00 for a first year production...
Your Winchester model 1907 chambered in 351WSL(Winchester Self Loading)and was made in the last 3 years of production will bring between 175-450 dollars,for a rifle showing between 10%-80% of its original finish,and a good bore.These rifles were made from 1907-1957.
Try e-gunparts.com
The Old West Scrounger usually has some.
50-500 USD or so
Ammo for your .351 can be had at Old Western Scrounger. Go to www.ows-ammo.com and click on ammuntion.
Winchester made some that did. Remington also, IIRC.
Find a copy of Madis' book.
The collector value can only be assessed by a visual inspection & evaluation. Old Winchesters are very much like old classic automobiles... the graded condition and factory originality are the key factors in determining what they are truly worth.
Value depends upon the original grade of the rifle and it's current condition. Winchester had different levels or grades for rifles, plain or deluxe. The deluxe version would have advanced checking with better quality of wood. The current condition of the wood, rifling in the bore and percentage of blueing, will need to be evaluated before a value can be placed on the rifle. Either take it to a gun shop or post detailed pictures.