70duster 360 gets hotter the faster i go

Ill take it for a spin and let the heat soak up, then do another temp test and write it down... I jus gotta b quick cuz it cools down quick idleing...pullys are stock, the larger ones, i seen pix of the smaller pullys for ac, and i kno belt is tight and new belt...
Im leaning on the pump isnt working right... I have blasted the radiator with the garden hose, and it dumps water out the bottom hose.... I kno that stock pumps have a pretty big gap behind the impellers, wich wud let the water go wherever it wants to i guess... But then why isnt everyone having this problem?

Im with u on a dizzy with vacuum advance for a street car... But i jus dumped like 450 bux on this dizzy and the 2 sets of diff wires i need to clear my wounderful headmen headders...so im tryin to run it if i can