Okay, I'll throw out my favorite for these types (older flat tappet) engines
Plain 'ol Delo 400 15-40w
Zinc/phos levels are as high as any of the expensive 'syns' and 'racing' oils
Never had a wear issue in many-many years of using this product.
... you can buy it a very
good prices at any Costco, Sam's/WalMart or common chain auto stores like NAPA and the others.
btw - the 'base stock' processing is the same as most the "Synthetics" ... Group II+ & Group III ... and has the same Moly/Boron additives common in 'syns'
It's the perfect trade-off wieght for these older engines with slightly larger clearance specs than the 'newer' engines.
There's no great gain to be had with a full/semi syn in these engines, wear patterns are aready well developed and they are prone to having ring and piston clearances that allow higher than normal oil bypass to the combustion chamber - leading to higher than 'normal' modern engine oil consumption ...
I've been using it in all my regular oil applications for many-many years (since Valvoline started dropping their Z/P levels) and have not had one bit of problem with it.
I run it in Large (500+) C.I. boats and trucks and other high-demand uses and the engines perform flawlessly on it.
ps: While at you local NAPA store, pick up a "NAPA Gold" oil filter for it - best there is