I have the GM Performance Parts 425 horse 454. I have been running about 10 degrees base timing but I just read a GM tech sheet for the engine that says to use only 4 degrees. Should I go with 4 or stay close to 10?

If it doesn't ping and it starts fine, then leave it. I run 15° initial and 35° total all in by 3000 rpm. I don't have any vacuum advance.