i am using kohler magnum sae30 it has a API rating of SH which is about as close as you will get to the SE that is called for in my 76. to boost the zddp content further i also use delco engine oil supplement. i mix 5 litres with one bottle of the eos and keep it on hand for the occasional top up. i am fortunate that my car has never had modern oil in it as it was in storage for 17 years before i bought it. so, it has always had adequite zinc content .
We had our L78 Chevelle on the road for 13 years and 37K miles and always used regular name brand oils off the shelf with a bottle of EOS. Never had a problem. With our 2005 GM recommended Mobil 1 5W30 and GM oil filter so that's good enough for me. Our lawn tractor has a lot of years on it and, when it was cold in the fall, would smoke when started using standard 5W30 oil. When changing oil this summer I used the Mobil 1. I was totally surprised. There is zero smoke at start up. I surmise that the Mobil 1 doesn't thin out nearly as much when cold and the rings can control it better. Whatever, I'm happy.....and pleasantly surprised too.