I run flat tappet cams in all my engines and use VR1.
But.........I have been working on these cars for years and years and personally have never seen a worn out flat tappet cam or lifters except on the Chevy 305's that all had bad heat treatment or metallurgy on their cams.
I also have ran cheap Walmart oil without any additives on flat tappet engines for past 20 years without any problems.