Improper engine break in.

What's a good weight to run a stock clearance 360 hot smallblock? I've been using VR-1 30 straight weight with good results. However, 30 straight weight is getting harder to come by. I live down south in San Antonio, Texas which summers can be brutal and cold mild to cold but is short lived. 10/40 or say 10/30? 10/30 is thinner than 30 straight I would think?