If your mopar is you daily driver!

Engine temp? At a normal operating temp. could vary by engine and weather. Do you need heat? The normal 195 stat is probably in there. A cooler running stat may help. Again, "May" help. Same with spark plugs. Een high performance street cars, a normal stock plug is all you'll need. A cooler or hoter running one is not going to help mileage in a bg way, but then again, if you find it does, it'll be minor. Just like many of the things above....which add up.

Fresh air from a scop is an excellent idea. But a foward faceing scoop dont do much for areodynamics/mileage. A rearward cowl should help that. All in all, fresh air to the carb should be cool as possible without restrictions.

On my 400, I have a small primary TQ. The large primary TQ had more pep. But the smaller TQ has super throttle response. It does require a further push on the gas pedal though. The 3.55's aint helpin much.
I have run the 600 Edelbrock on top. It had great primary operation but found when the secondaries opened up, it only seemed to make alot of noise and go no faster than the primaiers alone did. I did not have a chance to tune it though.