What you need is the table in the back of the book "Weldability of Steels" by R. D. Stout. I don't have my copy here at home, or I would look it up for you. ASME IX lists A814 as a P-10C, C-Mn-Si steel. Tensile strength is in the 70 ksi range. I'm not sure what sets this apart from a P-1 carbon steel. A good source of info on weld material selection is the folks at ESAB in Hanover, Pennsylvania (formerly Alloy Rods). You might go to their website at www.esabna.com, find their toll-free number (or direct at (717)-637-8911), give them a call and ask for technical support department. I have found them very helpful on similar questions in the past.
Marty