GM cars range from 1350-1450 . corvette pumps up to late 70's early 80's are 900-1000 . vega's and the like are 750-850 . the corvette pumps work fine with the thunderbird tack. ford racks run 900 or so .

shims increase pressure , liter or shortened spring decreases pressure. . large hose reduces pressure small hose ( braided line ) increases pressure