These shotguns are selling for between 150-300 dollars at this time.
I have two Savage semi-autos. Although the long recoil action guns are very reliable and wonderful shooters, they have almost no re-sale value in today's market. Mine are both in 90% condition, and I bought them for under $200.00 each. Remington model 11 parts interchange with a lot of the model 720, 745, 755A and 775A parts.
A Savage 745 is essentially the same design as the Browning Auto-5 and looks a lot like it. The big visible difference between the two is that the 745 does not have the magazine cutoff lever on the left side of the receiver like the Auto-5.
the 745 was made from 1941 to 1949, but other Browning A-5 variants were made until 1999
If your model 400 is a semi auto shotgun, with a squarish back to the receiver (something like the Browning Auto-5) these were made for Western Auto by Savage/Stevens/Springfield, and should cross reference to the Mdl 745. The e-commerce side of gunpartscorp.com has a schematic for the Savage 745/ 745C, see if that looks like yours. They DO have some parts available if needed.
Savage 745 Golden.
The 745 is a simi auto .
The serial number is located just forward of the loading port on the bottom of the receiver.