You can find parts and/or a manual for an Ithaca Model 72 saddle gun in 22WMRF on many gun websites including GunBroker.com and GunPartsCorp.com. You can also find these items online at DiamondGunSmithing.com.
There is an online source, Numrich Gun Parts Corp - http://www.gunpartscorp.com/
Numrich Gun Parts Co. http://www.gunpartscorp.com/catalog/Products.aspx?catid=4170
Try e-gunparts.com
http://www.diamondgunsmithing.com/index.html
I cannot find a serial number that high in any of my Ithaca references. The link below will take you to a good summary of serial numbers for Ithaca shotguns, you may be able to find your model and date there-
i am looking for a canon 28 feet a gage 12 xl900
your Ithaca model 37 is made in 1966 look on WWW.SURPLUSRIFLEFORUM.COM look for in the "search engine" on that web site type in ITHACA 37 DOM there you'll find the Serial Number chart
The logical place to look is at your local gunsmith's shop. You can probably get the parts you need online.
You have an Ithaca Flues model made in 1915. Can not provide additional information without the stampings on the watertable, barrel flats and overall condition.
Watch www.gunbroker.com under "Ithaca"
1947