Classic/Antique Car Repair: Fill Radiator, water coolant, radiator cap

Question
I have a 1975 Mercedes 450Sl.  It gets hot easily but has a new water pump, hoses, and everything else under the hood.  I can't tell in my manual how high to fill radiator reserve. It has two marks.  One halfway up the reserve and the other at the top of the reserve.  It was empty so I filled it to the halfway mark with a '50/50 add water' coolant.  I didn't put water in only the coolant. Should I add water?  Sparklettes?  

Answer
Cherie;
HI well I would put in some 100 % full coolant and fill it to the second line, no more, no less. the  (most) it could do is spill out. if you are overheating and changed all of those parts = did you change your thermostat and replace the radiator cap ? as that can cause you to over heat.  ok