This is more and more the sensible way to go when upgrading or replacing the front sway bar mounts.. you replace them with new brackets & if you choose.. go with these greasable units that are supplied in complete matching pairs.
Choose the size you need.
These are GREASABLE "D MOUNTS & BRACKET ASSEMBLIES.... - often cheaper then just the GM bushes alone..."
Most 64-70 era cars used from 5/8th to 1 inch, then early 70's moved along to 1 1/4", early and mid 80's they took as step back to 1 1/8 going to 1 5/16".
Most 72-81 Firebird TA & Camaro are 1 1/4 inch
Most 68-82 Corvette are 9/16" front,
- Measure yours if you do not know the thickness of the bar.