kz550 1988 leaking oil bottom casing

hi just put my kz550 1988 engine into a z500 frame, the kz550 engine is leaking oil from the lower casing through some holes that look like some kind of mounting plate, i have blocked the wholes but what is meant to go here to stop this properly is it a sensor insert of some kind? i have to parts for this . photo attached

please help if you can i am a newby

I hope that's not for a oil cooler.
Steve

Thank you so much i beleive it is

Don't run it like that. Might starve the engine of oil.
Steve

Cool i wont , had a z500 1980 but had to replace the engine to a kz550 1988 to there a few difference ,
Had to convert it from shaft drive to chain which took abit but thats all good now ,

Hoping to have her going soon but all these things keep poping up ,

Ill have to get and oil cooler now more $$$

The orginal engine went under flood waters and sat for a few years so was dead dead dead.