dont forget, 1979 is exempt from new emiisions. it just has to pass the old idle check. so long as you get your timing and mixture settings right at idle, it shoudl go striaght through. cats on them trucks didnt do to much anyhow. if you are in good tune, i dont think you'll have a problem. just make sure they dont put it on the dyno, they tried doign that to my brothers 78 .... they cant ...