1970 duster stalling problems

hey guys I have a 70 duster slant six that I just got from el paso tx and I'm in Harrisburg pa, and it stalls 1/10 times when I come to a stop could it be from the altitude change? in el paso tx the altitude is 3.470' and in Harrisburg pa its 320' and if it is from altitude how can I fix it? if not anyone got any ideas how to fix it?