are you looking at a single pipe overflow, two pipe, or bean animal?
the reason you would put a standpipe in there would to bring the level up to just under the weir so you don't have waterfall noise. you can easily adapt to the bulkhead threads with a thread to slip adapter then just dry fit the pvc pipe into that. this also keeps to a minimum the return volume going to the sump when the pump is off. if you prefer, you could just throttle the drain so that the height in the overflow stays high and leave enough room in the sump to accept the volume in the box if you lose power or turn off your return pump for some reason like feeding.
