Rt6 is a thin 40weight and a fine synthetic. That would be my choice in your 5.0 if I felt I needed a higher end synthetic. Only prob. Is it come in gallon jugs so you would need an extra quart. Qsud comes to mind as an equal to any other synthetic off the shelf that's great and better priced.
I overlooked where you said u wanted to run dino I would suggest Valvoline 10w40 in the white bottle is a very robust oil and will do a fine job for your engine. Yours is the kind of condition valvoline is best for. An oil with a solid film base.
It caused a minor leak to be a major leak. I changed to another product for several oci and then tried it again and same thing. I wrote it off after that. Guys it's just oil I don't like it because of my experience with it that's all. U can do what you like