I've not seen a factroy magnum timing specs.
Stabbing:
A. 5.9 Magnum distributor would be emissions era, and although helped by catalytic converters, may have still used a relatively retarded initial to reduce CO at idle and maybe also to insure less leftover HC. Cats are damaged by 'raw gasoline.'
B. Cylinder head and maybe the cam and intake distribution is more efficient than the older LA, therefore the flame development and pressure rise is probably a little different.
The effect of the idle emisions game on timing is pretty apparent when comparing two exact same engines with and without an early CAP.
Take a look at the acceptable 1967 timing curves shown at the bottom in this post: Timing Marks on the 273 [66 Barracuda]
See how similar they are for the driving range even though one distributor begins 5* ATDC and the other at 10 BTDC?
