I bought mine from SD Performance 604 490 2211. Dave will explain the internal balance.
Engines like chebbies are balanced via the flywheel and harmonic damper, Pontiacs are balanced internally.
Where on Vancouver Island are you? The guys at Central Island engine and machine in Duncan will be able to help you out as well. I had my 428 on there dyno, they tuned me an additional 50 HP.
Ours are 166 teeth some ,like luk. have a 153 tooth and a 168 tooth.
Pontiacs made in Canada like the Beaumont and the Acadian had chev engines. Our Firebirds were made in the USA and have Pontiac engines. Some manufacturers think they are all the same and we get parts we cannot use.
You're better off consulting a Pontiac specialist like SD Performance, or a speed shop like Central Island than you are talking to someone at a parts store counter that has never seen a flywheel.
I hope you're putting a new clutch in with the new flywheel, make sure the bolt pattern and diameter are matching. Some are 11" yours should be 10-5/8", unless it's been swaped out before now.

Welcome to the site. There's a few guys on VI with Firebirds, some visit this forum some don't. They may be close enough to you to help you out if you need.