If you aren't worried about authenticity for shows etc you can get replacement cables from most auto-part stores. The gears you can get at Ford dealers, how many teeth hopefully someone here can tell you, or give you the formula you need to calculate it.
Once I ordered a replacemnt cable from a Mustang shop because it came with the gear, when it arrived I saw it was the exact same cable I could get at Hi-Lo's except they charged more than double for it, plus the gear was missing. I then got the Hi-Lo cable and went to the Ford dealer for the gear and returned the expensive cable back to the shop for my money back - no restocking fee as it was missing the gear.
69 Sportsroof, 351C, 4spd toploader, Restomod BOSS 429 clone - the one and only (?) 1969 BOSS 351