I also saw one of the World Series games there in 1974. Like you I would take BART there and walk on the overpass over to the stadium. Normally I would pay $2 for a bleacher seat. Some day games were poorly attended (2,000 or so fans).
You can still BART to Howard Terminal, or you can walk over from downtown.
It took several transfers . We’d get to Oakland and transfer to get across the bridge to the bus terminal in SF, then it took I believe another transfer , (it’s been 50+ years ago). There were four of us ranging from 14-8 , we always felt safe, safety in numbers.
I recall coming home from one game, the Giants had won, and on our trip home we saw them dropping off newspapers at the news kiosks with the headlines saying the giants had won, hot off the presses. Chronicle , Examiner, Oakland Tribune . Not sure if any of those papers survive in paper copy.