my cars spark twitches on short runs, and cuts out completely on log runsl

[seinsmeld]

when im driving my car around the block or for a short period, the spark twitches, when im driving for a long period and doing about 120 km/h. it cuts out. only the car dies. the radio power windows, everything else is fine. I changed the interior over from a 1983 to a 1992, along with the harness. I changed the multi switch, changed the starter switch. im running an hei distributor, with a holley tbi. its a 347 stroker motor. I have no idea what else I can look for. any ideas? thanx

[ZR]

Explain what you mean by "spark twitches"?
Does the HEI interface with the Holley TBI or are both stand alone?
When it dies, what do you do to fire back up?
Did this all happen when you changed the interior or having problem before?

[tulowd]

My engine would cut out intermittently a while ago. Switch key on and off it would usually work again. Suspected a broken wire in the harness from the ignition switch to the MSD box under the hood. Ran a new power wire from another place and voila - no more cut out.

[seinsmeld]

twitches, u can feel it cut on/off quickly. both stand alone. just got them in sync the other day. sometimes it sits for 10 min. then fires back up. just when I changed the interior, put a new motor installed the holley tbi.

[seinsmeld]

u can feel a brief drop in voltage, like a hesitation but not vacuum is what i mean by twitching