Any Heavy Duty Engine Oil (HDEO) will have more than enough ZDDP for flat tappet engines. It is actually the phosphorus in the additive that provides the anti-wear protection. The older CI-4/SL versions have a bit more than the CJ-4/SM oils but, since the specification is performance-based and backwards compatible, the latest oils will work fine, especially in engines that are in stock or near-stock condition. HDEOs have better cleanliness additives than racing oils (like VR-1) so they can easily run longer than 3000 miles and keep your engine cleaner.
There is no need to use a 40-weight oil (10W-40, 15W-40, etc) in an good-running engine that originally called for a 30-weight oil (30, 10W-30, etc). If you want to stick with a dino-oil,
Shell Rotella T 10W-30 (CI-4/SL) and
Brad Penn HDEO 10W-30 (CJ-4/SM) are readily available. Synthetic 30-weight HDEOs are available too but, because they flow so well in cold temperatures by their nature, are available as 0W-30 and 5W-30.
ACCCC Engine Oil Article