1991 Chevrolet Astro Q&A
1991 Chevrolet Astro Question: Did the 91 cargo van come with a Vortec engine?
This site can help you answer that question and more about your Astro Van: http://www.goodwrench.com/Downloads/index.jsp - Bret Bodas
look at the engine digit in your VIN number. (off hand cannot remember if it is the 8th digit or the 10th, one will be the engine code, the other the year.) if you have a "W" code, you have the Vortec. The other code for that year (non-Vortec) in a 4.3L IIRC is a "Z" - Wilsonite