Since you suggest needing two, it seems that you mean tracks for the
jib sheet leads, which run for & aft, rather than travelers, which run athwartships for self-tacking
sails. If you are concerned about the cost of snap shackles, what about the cost of cars for the tracks? Screws will not
work well in this application. They will likely pull out and/or leak abominably. Besides needing bolts, you may also want to beef up the
deck where you place the tracks by replacing any
core in the deck with something solid. People often use
plywood or Starboard for this.
Backing plates or large
fender washers would also be a good idea. You will need to have access in the
cabin in order to do any of this.