count the track clips and multiply by the distance center to center between them (track pitch). That sled will most likely have a 2.52" track pitch. Other track pitches would be 2.86" and 3.0"
Like rd99 was saying.
Find the Part number on it. usually starts with 541 on Polaris tracks of that era. google track and that number and it will come up. A lot easier than guessing by pictures that can be deceiving.