Evening
Your set up and plumbing will dictate how and what to attach to the bulk head. I am not sure what type of bulkhead it has. Some are threaded on the inside so you can screw in a male fitting, some are meant to glue in fittings/pipes. There are also vacuum hoses that can be pushed in to use as a drain.
A few thoughts,
HOB overflows are good if set up correct and tested to handle any situation. Power outage, blocked drain, loss of vacuum in the tube all should be tested for.
If your able, to drill the tank it would be better.
Describe your tank, stand and sump and then we can the fill in the plumbing