My 72 Dart Swinger

Depending on what pump went in, that may be correct. It should drop down to about 40 at hot idle. The oil you're using will make little difference in the pressure, especially if you're thinking it will make 40 psi difference.

Don't forget. ZINC and MAGNESIUM have been removed from conventional oils and will cause catastrophic cam failures if you run them. Use a full synthetic. Mobil 1, RedLine, Amsoil, (maybe) Royal Purple, OR you can use Rotella.....yeah, what is used in Diesel trucks.