Tom,
I use Valvoline 20-50 racing
oil in both my big block and stroker engines. That is what they used to break the stroker in on the dyno and I have used it in the big block for over 30 years with no problems. I am sure there are other oils just as good but I have just stuck with what has worked for me and the engine builder of the 351 stroker said that is what they used in their race cars. The other guys will also have a lot of good oils that they can tell you about.
Ron61
Ron