I'm sure you will get a thousand opinions on this, so I thought I'd drop my two pennies on the pile. Like Ron61, I use 20W50 Valvoline in my engine on instruction from the builder. I have always shied away from straight weight (such as 40 weight) racing
oil because I have been told by folks smarter than I that it typically lacks many of the longevity and anti-corrosive additives of normal street-engine
oil. That's because the refiner assumes you're going to change the
oil after each race, and so it doesn't have to last very long (from a chronological point of view). Also, unless you have a pre-oiler installed on your car, the startup wear on the rotating components may be rather high until the high-viscosity oil warms up and begins to flow.
As to the protection capabilities of 10W40, I can only relate my personal experiences of driving a 1970 Vette 350-350 for about 12 years and accumulating 140,000 miles. The car was driven in weather between Florida summer heat and Ohio winters during the time I owned it. I used Quaker State 10W40 Deluxe exclusively on that engine, changing oil and filter every 3000 miles. At 95,000 miles, we broke the engine down for a freshen-up, and could still see significant portions of the original honing marks on the sides of the cylinder walls. The marks were worn off in the center of the stroke, but could clearly be seen over the upper and lower 1/3 of the stroke. I agree that the 0W multi-vis are probably not suitable for most areas of the lower 48, but the 10W oils are OK for most applications. My opinion and experience, FWIW.