I have one of each. The shorter of the two uses a 5 inch carb hole on its base. I have owned one other short type dual snorkel and it too had the 5 inch carb hole in its base. In 67 some c bodies ran holly carbs which had the larger dia. The taller of the two 67 dual snorkels i have uses the smaller 4 1/8 carb hole in its base for AFB which is what the R/T's ran