Your Winchester model 1907 self loader was made in the year 1923,with the serial number that you provided.
Try e-gunparts.com
50-300 usd
Ammo for your .351 can be had at Old Western Scrounger. Go to www.ows-ammo.com and click on ammuntion.
50-500 USD or so
The Old West Scrounger usually has some.
The list of numbers that are divisible by 351 is infinite. The first four are: 351, 702, 1053, 1404 . . .
Winchester made some that did. Remington also, IIRC.
Serial number
A True Woman has 351 pages.
1, 3, 9, 13, 27, 39, 117, 351.
The partial VIN should be stamped on the drivers side back of the block just below where the head mount.