I have a 88 7.4 putting back together after a couple years and on the oil pan there is a drain plug and the otherside has a brass fitting for like a oil cooler line but can't figure what goes there . Thank you

Might have been for a line to an oil change pump or drain hose to the garboard plug? What size line/fitting we talking about?

Oil drain

The second threaded hole can be used for an oil temp sender or just plugged with a brass pipe plug.

its for the dip stick