There are a lot of factors that go into determining the best oil for an engine. In fact, there are so many that it's easy to overthink it.
If you're running a stock(ish) engine, somewhere between 10w30 and 20w50 is going to be your target viscosity depending on temperature, and with a flat-tappet camshaft, you'll want to make sure it has plenty of ZDDP (most people just call it "zinc", as that is the main ingredient and what the "Z" stands for.
Valvoline VR1 and Shell Rotella are both readily available and have the zinc needed in the correct weights at most parts stores. (I myself run Rotella 15w40 in my car). If you want something cheaper, you can buy the quality oil of your choice and add a ZDDP additive.
If you want a syntetic, Royal Purple has what you're looking for on parts store shelves, or you can order oils from Joe Gibbs Driven and other performance oil companies. There is also Amsoil, which is available from independent dealers.
If you really want to go down the rabbit hole on this, the forums at bobistheoilguy.com are a treasure trove of information from experts, enthusiasts, and the frugal among those of us that do our own maintenance.