sputters after 10min of driving only on Hwy

I have had this problem eversince I owned the car. It has 420a powerplant n/t. It will drive fine in town at around 30mph, once I get out on Hwy after about 10min it will sputter and eventually slow down and die. Also it will sometimes stall at stoplights. Im sure there are other posts just like this but I couldn't find one. Plus the computer is shorting out and I don't know why.