Don't forget Mobil 1 15W50. It is about $26 for 5 quarts at Walmart. It has high zddp and is full synthetic. It is higher weight, but because it is synthetic it will still flow good at lower temps. I wouldn't likely use it in Canada or Alaska in the winter time, but for anything warmer than that I probably would. I've been using it for around 10 years on my solid flat tappet engine with 405 lbs open spring pressure.
JMO,
paulie