Hi Hemi,
for $20 you can buy a replacement azimuth pin that is fixed with a nut so you can simply drill a hole for it, rather than tapping a thread. A quality tap and the right drill bit for it will cost more than that...
https://www.siderealtrading.com.au/p...justment-post/
Or if you want to spend a bit more, buy a whole new adapter plate including pin and simply bolt it on top of your pier:
https://www.siderealtrading.com.au/p...adapter-plate/