[mr0077]

El, David is right, the shroud you have is compounding your cooling problems, take it off. In general (with electric fans), the air should flow through the whole radiator when moving and get pulled through the electric puller fan when idling. A tapered shroud (which you don't have room for) might let air move through the radiator and through the fan, but at speed the air hits the flat surface and it just blocks air flow.
On timing, if you have the timing too retarded, it will overheat, particularly at idle. When the mech and vac advance come in at higher revs it will "solve" the problem a bit, but you would likely know something was wrong, 'cause the car would run like a dog if it was that far retarded. Still worth checking...