Tire size bagged 64 20X8 wheels???

[fast&low]

Hello guys this question is for a buddy of mine not for me.
My buddy just picked up a set of 20x8 Dodge steel wheels re-drilled 5 on 5 for his 64 C10 fleet side he plans on bagging it in the near future so my question is what would be a good tires size for that set up? He won't be laying frame just a mild bag kit.
Don't know if I asked all the right questions or gave all the info needed?
So if there's anyone out there running the same set up any and all information would be greatly appreciated.
Thank you for looking & your time