Distributor vacuum advance hitting intake.......

I've seen 2 different sets of directions about the subject of the slot on the distributor drive on a small block in different year FSMs. I don't know if it was a year thing or or if it was a car/truck thing or a body style by body style thing.....
Some say that the slot needs to be pointed at the front intake manifold bolt on the driver side (#1 cyl) and somewhere I seen where they showed a pic of the slot going directly front to back, parallel to the line of intake manifold bolts on the driver side. About the difference of 1 tooth position on the distributor drive.
Each of these were referenced, with #1 being at TDC. At this point I won't get into "TDC on which stroke"