The easiest way to see if a coil-in-cap HEI is from a V6 or an Inline is to look at the distance between the shoulder where the clamp holds it into the engine or manifold and the underside of the main body. The Chevy 90 degree V6 unit is 1&3/4 inches ( exactly the same housing as the Chevy V8 HEI ) and the Inline unit is 4&3/4 inches. Another way is the V6 unit doesn't have a small shaft hanging out of the gear to drive the oil pump like the Inline does.
I have done several 200 / 229 V6 Chevy HEI's and Inline HEI's with the coil-in-cap and they all use the same cap. Stay away from any parts that fit a "Buick" or "odd fire" and you'll be ok, even Buick got away from them after about 18 months production - 1977 / 1978.
