What's the best oils for tappet cam engines?

I went shopping for oil a week or two ago. I had used Kendall 20w50 GT1 high performance in the past and after looking at all the high ZDDP content oils and bought another case of this. Valvoline and similar were 5.99 a quart but the ZDDP was $3.18 a quart.

Extra $2 to $3 a quart costs me $18 to $27 more an oil change with the high capacity oil pan...Gas is already killing me!