Clutch Fan

Can you elaborate on DERALE setup ... I am installing a big block in my 69 dart with a 22 almost 23 inch across radiator and 18 inch tall.. My issue also is possible interference on water pump pulley to fan contact .. SO i opted to go with dual fan setup due to more room in center of radiator with dual fan setup ... I called b-cool and they recommended p/n 75007 dual fan spal setup .. Does ANYBODY know how what dual fan setup works with a large tube 2 row radiator works ?