Greetings , I  swear by Brad Penn in my  Mummert 292 for the last 13 years .
The motor has  finished  seven  la Carrera Panamericana  & four Chihuahua rallies and has  never been  rebuilt .
These endurance rallies are long 10-12 hrs a day  ( LCP = 7 days  & CH = 3 days ) and we push all day .
and have managed to always finished  1st or 2nd in class .
see their web site  and available thru Summit , Amazon  etc 
giddyup
 

It would seem an easy inexpensive solution is to use whatever modern oil one prefers, and simply add a small bottle of the ZDDP additives available.

Except, oil engineers strongly caution against aftermarket additives. They point out that motor oil additive packages are carefully blended by the manufacturer, and that third party additives can cause problems.

I've decided not to worry about it, a stock motor as I have w/ OEM camshaft has mild spring pressures and aren't going to have the risk. If it were a problem, it would have shown up by now.

You make a good point. Add the zinc to regular oil and ''DON'T WORRY ABOUT IT", like they say in New Jersey and New York !!!!
Late,
Tim 
Waiting Room For Heaven, Florida 33706

No, just so there's no confusion here what the engineers are saying is adding an aftermarket bottle of miracle zinc to the crankcase may cause more harm than good. We're not oil engineers so we kind of have to take their word for it.

I've been running a stock Y for 20 years now wouldn't it have shown up already?

tedster is on the right  trail.2years ago i sent 2 members a survey on modern engine oils,a engineer in ca tested many brands of oils results wher interesting. his summary is modern oil for flat tapes  lifters are fine for blocks and other flat tappet cams. the hot rod preacher received i package with all the tests. diesel lub is a absolute no fn way for flat tappet cams. it is designed for roller lifter diesel engines using low sulphur diesel. in fact the cat dealer i worked for sent memos to employees do not use rosella t on flat tappet cams(the bulk cans  of shell even  hade a caution (do not use on gas engines.
most block issues wher from  poor oiling to top end. if you have 1/2 the rockers getting  little or no lubrication  you loos camshafts,wear rockers and rocker shafts. my present 292 with 4vmanifold dura spark  sign,many miles blocked bleed tubes at rock shafts,idels  hot 20 psi 4000 rpm55psi,engine was freshened 12000 miles ago burns no oil(the od drip from valley cover). used pennzoil 10 40 never had to adjust valves.
OIL IS LIKE RELIGION/ OR POLETICKS EVERY 1 IS A EXPERT. NO 1 WANTS TO READ THE ENGINERS REPORT. JUST COULD NOT STAY OUT  OF THIS BULL SHIT ON OILS THAT SAVE THE DAY