The oil filter on a 1999 Chevy Blazer with the 4.3L Vortec V6 engine is typically located
on the passenger side of the engine block, towards the front. It's usually fairly easy to access from the top. You might need to remove some plastic engine covers for better visibility.
However, a picture is worth a thousand words, and a quick online search for "1999 Chevy Blazer 4.3L oil filter location" will yield many images showing the exact spot. This is the best way to confirm.
