Don't be shy to call your welding supplier. Often they are are great resources when determining filler metals.
We weld A517 with SMAW 11018, that might be a good starting point if you don't need a high volume. Otherwise the Lincoln sells a ultracore 121K3C-H that might work in your application.
As already mentioned we don't have many details on what your application is, but these might be a good starting point.
If you gave us more information we could help more. PWHT, Thickness, impacts?
Regards