Tony;
I don't know a whole lot about Cleveland engines, but 10 psi at idle and 25 psi at speed sounds way too low to me on any engine......
I have used at least four different brand oils and weights as well as
synthetic oil and my
oil pressure did not vary more than 5 psi from the different oils....I presently use Mobil 1 15/50........
I would install an
oil pressure gauge that you know works well or you have tested and check the oil pressure before doing anything else.....then go from there........
David