Probably is the pressure sender, I've never heard of an oil pump to let you know it's about to fail. They just break
I used a N1 oil pump with remax gear set and I'm hauling close to 400 awkw. The gear set is around $450 delivered plus
N1 pump, it should all cost around $550,
you will need to put a restrictor in the head though, and it's motor out job
Good luck