The 96 Chevy Blazer does not have a timing belt.
Your 1999 Chevy blazer doesn't have a timing belt.
The 2003 Chevy Trailer Blazer doesn't have a timing belt.
Timing belt
The 2000 Chevy Trail Blazer doesn't have a timing belt.
It doesn't have a timing belt.
Timing Chain
It does not have a timing belt, Chevy did not use timing belts in there truck engines.
The 4.3 liter V6 engine in a 1997 Chevy Blazer has a timing CHAIN
4.3 has a chain
Nothing, it doesn't have a timing belt.
The general time to do so is around 100k (100,000) miles