[Kenth]

1966 #1111090 389 2-bbl distributor has exactly the same centrifugal timing advance as the 1966 #1111078 389/421 4-bbl distributor.
0-4°@960rpm, 12-16°@2000rpm and 20-24°@4600rpm. Add to that 6° initial.

They do use different vakuum advance though.
090 uses the #1116242 control, starts@6-8in/hg and provides max 20°@13-14,5in/hg.
078 uses the #1116243 Control, starts@8-10in/hg and provides max 20°@15-17in/hg.