SkiFreak
Crazy Person
Being a drain, the fitting would not need to withstand much pressure.The other option is hacking up the stock drain and creating a bead roll or welding a barb fitting to fit a 3/4" hose.
If it were me, I would just machine up a thin walled stainless hosetail with a parallel end (not threaded) and simply Loctite it into the block.
This would be the best method for not reducing flow too much.