Truck Studdddering during Driving

[troonman60]

I have a 70 chevy with a 454 motor with mechanic fuel pump and took it on its 1st long road trip (150 miles) since I have owned it. After driving for 30 mins on flat ground it studdered for aprox 15secs like it was starving for fuel but did not stall out and I was able to continue driving. This continued the whole way, the weird thing was once I started hitting hills big or small the problem seemed to happen more often, losing power for few seconds but never stalling out. I was wondering if u guys have any ideas on what might be causing this.