You’ll actually probably be losing grip as the night goes on, not gaining it. Especially if it’s a humid night, you’ll likely see a pretty slick track. The last night race I did was a few years ago but it was humid and there was so much condensation that the karts were actually covered in water every time we went up to the grid.
Same chassis changes you would do for any normal low grip situation. You’ll want to add grip. Wider front track, stiffer front bar, more caster, narrower rear track.