If memory serves me right 1975 was the first year for cars and trucks under 6000 lb reg. weight needed all the emissions crap ,1979 the weight jumped to I believe 9000 lb reg. weight as the new cutoff. If I'm wrong somebody will correct me. Hope this helps.
Mike (member of the PA chapter)
2010 F150 sc 4x4 xlt 5.4L
2005 Hd Softail
1999 Explorer (girlfriends car)
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