I tried to find a way to get 4 marines alive to the command center, but with running past the solo enemy marine, it could easily clip a marine you don't want to get hit. Micro is hard in Starcraft 64 because of seemingly random pathings and I suck. So I decided 3 was enough. The next part uses a couple timings all at once to push the mission forward:

(1) The final phase starts when 10 marines are created, can disregard the SCV requirement

(2) An instant barracks with an instant pointer progresses the fastest to 10 marines since 2 barracks would be slower

(3) The supply depot has wiggle room for timing since it finishes a few seconds before the ninth marine would be created

(4) When the barracks is finished, there should be enough SCVs created to barely upkeep 1 marine cost

These together create a system where marines are created ASAP with no downtime in production. This can easily be beaten by someone who either does this just slightly faster or finds a way to get 4 marines to the command center. Thinking about it now, I wonder if marines can attack slightly earlier from the piece of land east of the water. For all I know, the tutorial 2 base could be there, idk.