I ran a Poll over on Chevelles.com asking what people ran. They build some stout cars over there. By far the preferred oil is Valvoline VR-1 in the silver Bottle. When I say "by far" I mean 2:1 over Mobil1 which is in second place. I think that Poll is up to a few hundred responders by now, so it's a decent sample size in the hot-rod community.
http://www.chevelles.com/forums/13-performance/831521-what-oil-do-you-use.html
We are aware of that generation SBC having cam failure issues, but you did not say what cam is in it, or more importantly, what lifters are in it? And which valve springs?
The number one check is to pull the valve covers (one at a time) after the motor is warmed up and idling and check to make sure all the push rods are spinning, and at the same rate.
If all the push rods are spinning at the same rate, you are likely good to go for many, many thousands of miles.
If any are slow or not turning, you either have a lifter bore off-center or a tight lifter. Your cam is already gone for all intents and purposes. You could then pop the intake and swap a few including that slow one, to make sure they are not tight. But it is going down hill.
For Oil, I'd just run VR-1 10W-30. It ranks well in race motors and street motors and has no critics that I know of. It has plenty of zinc and a good stout add-pak overall.
Another option is Maxlife 10W-40 (red bottle). It also has a good add- pak, so a lot of less than ground-pounder engine guys are starting to use it as a readily available street oil they can get most anywhere. I call it VR-1 jr
Personally, I have always had good luck with 15W-40 HDEO's in warmed over engines. I have a few well over 200K running on Delo400.