Use the wider gap, 0.045. HEI stands for High Energy Ignition....
It takes more energy to jump a wider gap and thus, the energy in
the spark is more....plugs were gapped narrower in the last century
because the available energy was less and therefore, for a reliable
spark, the gap had to be smaller.

The spark plug gap dictates the energy delivered....not the
coil because only enough energy to jump the gap is required.
Of course, changing the gap changes your timing so adjust
accordingly.