I use Mobil1 and add one blue bottle of STP per 5 quart for the ZDDP.
My 68 GT350 has an 8 quart road race pan on it with an oil cooler. My Pantera has a 10 qt road race pan. Both have oil coolers.
The oil doesn't get changed from mileage. I change it by color change. Simply put, they don't get enough miles put on them for that.