IROC86CAM

my 86 305 tpi hesitates for a second after every shift and shudders when accelarating. if i back off slightly and try again, its ok. it does this going up a hill or slight grade too. at highway speeds it runs fine until i have to slow down to make a turn or stop light. then it almost stalls but sort of catches itself at the last second and idles fine. did the shop do something wrong installing my new speedometer, or is this something else? you guys have been very helpful in the past( woman at a garage things), so i thought i'd ask. oh, by the way, my tach bounces very slightly at an idle.