Rebuilt driveshaft, now engine is running rough

[Blooeffie]

Hello forum,
I had symptoms of bad u-joints, (clunking when put in drive/reverse, vibration at 50mph, visual.) so I had a shop r&r the driveshaft and center support bearing. On the ride home after the work was complete, my engine started running rough. I was planning on installing an under the cap electronic ignition, so I did this at home. After installing the ignition upgrade, The engine went back to running smoothly. All was well for about twenty miles, but then the engine began to run rough again. This is on a 1970 F-100, 360CID FE, 3speed automatic, no a/c, no pwr steering or brakes. Any ideas where to begin diagnosing this issue? Thanks.

[Madman]

First thing I'd check would be your vacuum lines, see if you have an intermittent leak.

[Blooeffie]

thanks for that advice. my vacuum lines are ok. I think this may be an ignition or grounding problem. I posted in the driveline forum because that was the latest repair. I was able to get the engine running smoothly for a while, but I am having intermittent problems. By the way, the new driveline is like butter. Amazing improvement in drivability and reduction in noise!