Anybody using Driven brand HR-2 oil in their slant?

Guys/Gals: My engine builder swears that this is the only oil to use in my newly rebuilt slant six in my 1974 Duster. Completely stock rebuild, not racing or turbo - ing it. Has anyone used this stuff. Pricy at $10.00 per quart. What oil do you use in your stock slanty? I've heard that off the shelf NAPA store brand oil is perfectly okay in these motors.

Thanks - cruiser