Anything is possible if you have the money, but, this is not practical to try.
If you are referring to the 33 round double stack magazine - I know it will fit the Ruger P-89. If the P-89 mag fits the P-85 your answer is YES.
Call Ruger 9287786555
Ruger.
No.
100-800 dollars
Ruger's web site has extensive sn data.
i have a 10/22 carbine .22 lr caliber ruger wood stock plain rifle theres a number on it 234-30732
Magazine
The Ruger SR9 uses a proprietary magazine.
Ruger's website has extensive serail number data on all its models.
50-200 usd
100-300 USD