The 28 oz imbalance, 157 tooth flywheel is the same for a 289, 302 and 351.
The clutch you bought was probably a 10.5 diapraghm type and it will not mount up to a stock 280z flywheel because it mounts a 10 inch clutch.
You will need a 28 oz, 157 tooth that will mount a 10.5 (if that is what...