GMC headlight upgrade issues

[jfnar]

I originally posted this in ELECTRICAL but got no response so I'll try it here.

I recently upgraded the headlights on my 68 GMC with the Hella 002850811 kit (https://www.amazon.com/HELLA-0028508.../dp/B001G7A9YS). I only changed the outside two lights and I did not upgrade the wiring or add relays, though I plan to someday. The improvement over the old lights is very noticeable but I have one issue. When driving with the brights on the lights will intermittently go off for a split second. It varies from a flicker to going completely dark for a full "Mississippi." It never did this with the old lights and it still doesn't do it when on dim. Last night I made a test drive and kept one eye in my side mirror to see if the side markers flickered when the lights did but they did not. It's not a daily driver so I'm not going to drive it at night until I get this fixed. Any suggestions will be greatly appreciated.

Jeff