I have a 1982 300sd
-Almost everytime i start the car i need it to be jumped, i don't know if this is due to the glow plugs needing extra power in the cold
-when i drive my battery light goes on and off
-i need a new water pump badly so i don't know if this is effecting it
-the belts are fine and so are the connections for the battery, no open wires or anything
- my radio dies when i'm driving, it turns on and off as well, probably due to the battery

should i just go out and get a new alternator or maybe get a newer more stronger battery like a marine battery?