1999 Chevy Silverado

I am having problems with my truck...It started stalling on me going down the road, this went on for about 40 miles (coming home from trip) it would stall then kick back in and run fine, well it finally dies and I changed the rotory cap and dist. cap, ran good for about a week, now it is starting over again. It stalls and then kicks back in and contiunes like that. Any clue what this can be?