Battery draining fast

Hard to see but if I have this figured out right per the colors......

The big wire has to run direct from the battery to the starter.

The brown is likely not a ground (if that was what you are asking); if it is what I think it is, it comes from the starter relay and carrires the current that activates the starter.

Is the smaller red wire jumping over to the starter relay big lug? It can come driect fromt he battery to the starter relay's big lug if you like, but if you have also run the alternator output direct to the starter relay's big lug, then when this gets running, watch for voltage pulsations from the alternator (like flickering headlights). That may not happen, just be aware of the possibility; small resistances in the charging system chain can help stablize its operation.

The lug on the smaller red wire is garbage!

Is this a 273 engine?