Yes you can. I believe you just loosen the clamp and rotate it until it only starts in the neutral position. You're correct the manual doesn't cover the adjustment. You need the Fordomatic Shop Manual for adjustments.
As a side note if/when you replace your neutral safety switch, replace it with one from a '57/58 it will tart in both Park and Neutral. Much more convenient IMO.
The way to adjust the switch is to use a 5/16 inch socket and loosen two screws that hold the switch on the bracket. Place the gear select lever in neutral. Now move the switch until you hear the contacts "click". Tighten the two screws being careful not to move the switch as it is being tightened.
Do not loosen the u-bolt clamp. The bracket at the base of the column will not rotate as it has "dogs" at the bottom that fit into slots in the column tube.
My '57 Skyliner only started in Neutral. I had to buy a 1958 neutral switch so that I could start it in park also. The 1958 NOS neutral switch costs about $35 or so on eBay.