I cannot help with specifics as to exact replacement of the CA8031 because I have been unable to locate any information as to pinning or specifications for this part number. The web searches on CA8031 turned up very little. So maybe you could give a few more specifics about this part.

You might want to check out if the DS2003 would work. This part is a DIP with pinning like shown here:


Note that this part is a darlington configuration with each driver and the output will only saturate to about 1 volt. This may or may not be a problem in your application. Note also that this part contains the protection diodes that are useful if the IC is used to drive inductive loads. You must connect the pin number 9 to the positive supply in your system. (i.e. do not leave the pin open). This part was originated by National and here is a link to the DS2003 data sheet.

I hope this helps.
Michael Karas