Yes, the Tadao board (and any AKA board for that matter) will work in a Viking. Only the second run or combo Musashi ones will work in Excals as well as the Tadao Ebisu. As far as WAS boards any 1.6 and older will work in both, but the 2.0 will only work in Vikings. The easiest way to tell which version you have is to turn the board on in programing mode, see how many parameters there are, and match it up with the different versions of the boards.
Tadao Musashi (Gen 1): Viking Only
Tadao Musashi (Gen 2 "Combo"): Viking & Excal
WAS (2.0): Viking Only
Was (1.6 or lower): Viking & Excal