Not sure about 2 between Cut Back and East Glacier but from East Glacier to West Glacier is not a problem.
East Glacier has few convienent CGs. The majority of the CGs are located at West Glacier. There are at least 10 CGs along Rte 2 west of West Glacier to Hungry Horse. A distance of about 10 miles. We were there the summer of 2007 and stayed at
San Suz Ed RV Park. We found it to be a nice clean park just 3 miles from West Glacier. One plus for San Suz Ed was we had a Verizon signal for both the cell phone and the air card.