If you have 0.40 gap you probably mean 0.040 gap since 400 thou is a bit much.
Yes, it will work but wont be as efficient as the correct gap. Like Denny said, with an HEI, use 0.045 or so. The extra gap allows a higher voltage to build in the system before the spark jumps the gap. The amount of energy is a function of the dilectric strength of the medium (air and fuel) and of the gap. This is why HEI is better, it has a higher energy capacity so the gaps can get bigger and therefore more energy it takes (spark energy). For a given medium, the energy that it takes to jump the gap has nothing to do with the ignition system....the volts are the same. However, how that energy is delivered does depend upon the system (rise time, duration of spark, etc)