Bone stock down to the manifolds and dual point distributor. 68 383 dart just curious what the initial timing should be. Thinking old specs was 0 degrees before tdc..that sound correct.
If its stock distributor then use stock initial.
Initial is set with a vacuum advance hose plugged and tachometer.
This is even more critical if the distributor was a part of a Clean Air Package (CAP), which it may be for '68.
If you don't have a '68 FSM, download it from Mymopar, or send me a PM with the distributor's tag number and I'll look in my paper copy.