As per post title...what type of fitting should i use? Sump is off engine

any as long as it has the right size hole to match the drain!

so i could just use a barb type fitting, then weld the fitting to the sump, and use a rubber hose with a hose clamp?

What engine?

Au has enough meat to cut a thread in the alloy. I used 1/2 inch BSP with barb fitting to suit my braided drain.

E - series can be done with a drill, punch and tap, but mos people I speak to reckon you are better off to have the sump off and weld a nut on.

either way, you will make it work.