Mine in 1987 had foam insert. So I would say in that era, yes.
Just hear-say, I was told that it helped displace water intrusion, personally I would rather be able to see inside the void than see foam. Was also told it increased buoyancy, I don't really believe that. Maybe if the bracket itself is not airtight then the foam will help.
Until I had a fabricator make mine AND bought Armstrong deck plates, I didn't have an airtight system. My springfield would not fit to the transom, at the top of the bracket, from port to stb. And the "deckplates", 2 pieces of flat plastic material with several screw holes to fasten to the bracket, was a constant concern for water seepage. Unfortunately if your plates screw directly to the bracket, the more you unfasten, the quicker the threaded holes strip.
Sorry to be so negative, hoping my troubles will be helpful.
Again, good luck in making the springfield bracket just that....airtight, as well as keeping a protective coating on it.