Lots of discussion about oil now days for use in old flat tappet engines. I am a Valvoline fan and use Comp Cams break in additive for more zinc to help keep my camshaft from going flat. Most racing oils have more zinc for that purpose too. I would stay away from synthetics.
I have been buying the Valvoline VR1 oils lately for the older engines
states on the bottle not street legal, so it has to be good
Claims it is high in zinc
They do have a 10w30 and until the end of last month buy a case get a rebate for the cost up to $50
Auto Zone had it on sale a few months back for $2.50 a qt. for conventional VR1 but in 50 & 20w50 only
if you use any moderen oil I would suggest adding the zinc additive
Mopar Collectors guide has oil they are selling that they claim had the needed additives in it for the older engines, also Gibbs racing and others have specialty oils for he flat tappet engines
I use 15W-40 diesel oil in mine, and many others I have to keep on the road. Its relatively cheap (where I buy it) and seems to have the extra zinc and detergents to keep the Dart ,etc., happy.