acceleration

currently running a carter 2 bbl setup on a 1971 slant six and 904 trans setup in my 65 valiant. i've noticed that acceleration is always a bit slow (granted, it's better with the 2 bbl setup vs the stock 1 bbl), especially when accelerating from a stop or traveling on a slight incline. i'm wondering if there's a way to improve acceleration via the transmission, like say, get it to shift faster? i'm not trying to race with it, just use it for normal city driving. it can get a bit hairy when i make left turns across traffic or freeway merges, because of the slow acceleration. any ideas?