Shootin from the hip here I'd say that you have to conform to the specification minimums for the materiasl you will be welding. If the material specs require yields AND tensiles then you must test for yields and tensiles, which I would suggest in any case. Ductility/elongation as well.
TheIowan,
Do we need Yield strength, Tensil Strength .....?
That is the million dollar question. Since it's impossible to match the properties of the steel, you need to determine what is acceptable.
Start with calculations on the expected load condition of the part. Based on that, then determine what mechanical properties you need the weld metal to perform. I suspect that you will need Yield Strength because your steel will see impact loads.
Tyrone