The front end of the cooling system will be quite standard , as outlined by Broljo above.
It is the back end of your system that is non standard and needs a total rethink.
I think you should separate the 2 problems, if you have water inside the car then you have a leak , either from the heater matrix (most likely) or hoses. Sort this first.
Once that is done I would run the inlet to the heater from the back of the head (as above. and the return is a single pipe on the opposite side of the head back to the pump.
Those both being done , now run a small bore pipe from the radiator filler overflow pipe to a catch tank and mount this either on the scuttle or the vertical face of the bulkhead. This can have a simple low pressure cap, and put a simple sealing cap on the radiator (as above).
That system worked well on my +4 race car and you don't need any more than that.
As above if overheating is still present, then look at the common causes of this, head gasket, liners crudded up inside the block, stuck thermostat, blocked or damaged radiator , slipping fan belt , ineffective water pump etc
