ZDDP additive

[HT413]

So, been reading some articles on the newer engine oils having less and less of zddp and or zinc, and the good stuff for older engines that run higher pressure valve Springs than today's motors.
I use Quaker State 10w40 in my 440 for years, but I am starting to wonder if I should be adding some zddp.
I e mailed Lucus and they recommended their muscle car oil or add their break in additive in.
No one sells this off the shelf around here, and the shipping cost makes online rather unpalatable.
In wandering around different farm stores and auto parts stores, the only additive I found that actually had ZDDP on the label was smallish 8 oz bottles of STP for 3.99 each .
?
Never used STP, always thought it was snake oil, all be it being more like Carmel than like oil.
Anyone have any recommendations other than bending over and paying for the shipping ?
Or am I worried about nothing ?
Thanks in advance

Couple years ago I used that stp zinc additive right after engine break in... and immediately wiped my cam. Motor had 40 miles on it.

 

[mopar73dge]

Thats what i use also, Mobil 15W50 racing in all my flat tappet engines.
In our bespoke racing engines we use for sprint(6hrs or less) Mobil 0W30 racing and for endurance(24hrs) Mobil 0W50.
Both have 1750 Phosphorus and 1850 zinc.