Ok so i asked around and it seems as though if it didnt come from the factory with one, you dont need one. Buit i know new exhaust has been put on there so how do i tell (or even more important how do "they" tell) if it never had one to begin with?

 

1975--catalytic converters were also made standard equipment on all trucks under 6,001 gross vehicle weight (GVW).

http://www.teknidude.com/blazer/history.html

 

So mosdt likely it DID come with one? that doesnt sound good.... i wonder how far id get just saying it didnt