Have that engine with Rochester 4bbl in the boat ,,, service bulletin
says:

1. Rotate engine in normal direction of rotation until the timing mark
on the crankshaft balancer lines up with "0" (TDC) on timing tab and
engine is in #1 firing position.
2. Look closely at the cam in the distributor. Three lobes have sharper
profile than the other three (sharp, round, sharp, round, ... 1 (132
dgrees) 6 (108 degrees) 5 (132 degrees) ... and so on ... )
3. Install the distributor so that when the rotor is aligned with with
the #1 spark plug tower, a rounded lobe is aligned with the rubbing
block of the breaker points.
4. Secure distributor with clamp and check engine timing with timing
light. For what it's worth I set my timing at 8 degrees and use Shell
Silver 89 octane.