Valvoline VR1 is available in straight 30 and is sold by NAPA and others. I have used it in many older engines with no apparent problems. I see no real reason to use a straight weight oil, it's what was available decades ago before multi-vis oils came to be. I run heavier oils such as 20/50 in the higher performance engines like the dual quad 409, the supercharged Cobra engine, etc. If you want a bit thicker oil, you can always add STP oil treatment which has ZDDP and a "viscosity index improver". A non detergent oil will not loosen up as much sludge or other crap you may find in an older (not rebuilt) engine. There are many opinions on oil, I just use what has worked for me. The cars I have here spend most of their time sitting, but get the best of care.
Gary.