I do have a warm 6 as well.....Crow 664 cam, mild porting, holley....3 core copper rad, can't remember the thermostat temp range and this doesn't get upto the temps you're referring to unless I have done some running and stop at lights at on a hot day....Again, tap water with that....
Yes, I'm referring to 6 bangers with my quotes but still yours still seem excessive with the quick temp rising you're reporting.....
Your oil pressure issues...Have you spoken to the old mechanic as to what oil viscosity you should run with the clearance on the crank you have?