1973-1980 frames are all the same,81-7 are all the same as well.They changed the mounts in 81.If your truck has a 73-80 frame then you need to use the specified years.If its a 81-7 it goes the same for them years as well.But if you got a 81 n up truck with a 73-80 frame under it you need to use the 73-80 mounts, vice a versa for the 81 n up frame as well..
thanks
Pat