Re: 350 stops for no apparent reason
When you wired it up did you replace the resistance wire from the firewall to the distributor? It's a (I believe) pink wire that goes from the firewall to the distributor to power it. Originally it went to the coil. This wire increases in resistance as it heats up and lowers the voltage to the coil to protect the points after warm up. You need to replace it with an appropriately sized non-resistance wire when going to HEI.
1968 Base hardtop 250 with a P̶G̶ built 2004r
Holley 390 CFM carb
Langdon split header to a 2.5" exhaust