Who was the scientist and who the historian of this "spooky" pair?
Paul Morse was a scientist who learned to transform himself into a silver age variant of Mr. Justice. Not at all connected (aside from costume and abilities) with the 1940's version, it would seem.
Of these two synthetic humans, which was known as the Shape and which as the Shadow?
The Shape was the yellow and black clad being designed to replicate any... well... shape. He aided lad Kevin Boyd on a tale involving some spies and then disappeared into the night, while hunted down by Kevin's uncle who was Shape's demented creator.
Bonus question: Which of these androids was replicated in the same issue?
This would be the answer to question #3 and the bonus question. The Blue Shadow was spawned by the evil organization known as P.E.R.I.L. to defeat the Shield, and almost succeeded until Shield used the same device to create a Red Shadow to combat his Blue Brother. Then both just waded away!