I always recommend full synthetic oils for gasoline turbo engines, and the Pontiac 301 is from the era before water-cooled bearing housings, so bearing coking can be a problem if cooldown time before cutting the engine is not carefully observed. But the slightly wilder flat tappet cam makes me want to recommend high-zddp oils, which do not exist in modern full-synthetic 30-weights. That engine originally specified 30 weight. Brad Penn 10w30 may be a good choice, but it is only synthetic blend. Rotella T5 is also syn blend, but Brad Penn is higher in zddp (1400 vs 1200). M1 5w30 has the Honda HTO-06 approval, but is low in zddp (800), but you can fix that with a bottle of ZDDPlus added to the oil fill. M1 10w30 High Mileage is a heavy 30 with higher zddp (1000). Or M1 0w40 has a whole raft of approvals in high power and/or turbocharged engines, and has higher zddp (1000) than M1 5w30.