I noticed my housings have some small corrosion holes about 1mm deep on the exhaust port, what can i do to prevent further corrosion? could i fill them with epoxy?

change coolant at the right intervals

gotcha, nothing i can do now? i dont think the previous owner ever changed coolent as i also spotted slight corrosion on the irons by the water o-ring, but thats not bad/ close to the seal yet.

you need to inspect the housing to see how deep the pittign realyl is it might not be worth using, also make sure that at the exahust ports there is no coolant burning thru if its in realylbad condition this could happen.