Is 426ci 360 a small block?

always wondered about that, I bought an 8 quart milodon oilpan, does that mean my whole system takes 8 quarts or do I need to add a quart for the filter?

You don't necessarily need 8 quarts in the system. 6-7 should be plenty. I run 5 total in my car with a standard pump. Running a little less helps keep the oil away from the crank and the extra from sloshing back & forth.