Not having an early engine bay in front of me to compare (but just going from memory and pics I see here), you'll have more height than I have in an Scout II engine bay, to mount a down-draft carb on that adaptor. That's one reason I'm going draw-through - no vertical room. Unless I could figure a way to pressurize a stock-ish carb and go blow-through.
In the old days adaptors like those were also made for the corvair - the outlet was triangular, though. Guys would put them on their buggies.
Since I have the rayjay compressor housing with that large 3" inlet, I'm thinking of casting an adaptor to couple right up to it, and slope downward while making a 45 degreeish turn so the side-draft runs crosswise in the engine compartment. I've discovered the "lost foam" method and hope to experiment with that this spring. Makes casting complex shapes a lot easier. Regarding using coolant to heat the base of that adaptor. I had envisioned doing this too, and believed that it would be possible to use one of those low-temp tvs to cut off flow to the adaptor (iirc GM used a vacuum controlled water valve to cut off coolant flow) at, say, 130 degrees. That way you wouldn't overheat the the intake charge once the engine warms up. I could see how such a simple modification could cut off flow to the 152t adaptor and maybe improve its function. The corvair simply used warm air to aid in warm-ups and prevent icing. If I can't improve my casting skills to include a core, I'll go this route.