Sorry to hear of the troubles.

Try a cobalt drill bit with lots of cutting oil and a very slow speed.

(Just in case #1 => The spec for the bolt is 65 Nm - that's just under 48 ft lbs)
(Just in case #2 => wagon W123 sway bars have a larger diameter than the other variants)

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!