I believe that the small block and big block sixes have different dizzies. The shafts are the same, so Pertronix units are interchangable, but when I was trying to find out more about carbs and dizzies I looked at a lot of stuff online and it seemed that the dizzies themselves are completely different for the 240/300 sixes.
It is unclear as well just how superiour the D.U.I. is. Certainly, an external box coupled with a DII dizzy will give you everything the Davis does. If you want the D.U.I. becuase it puts all the stuff together, nice and neet, then get an Ignitor II.
I called performance distributors once about my 240. The dizzy will fit, but they refused to even recomend it, as they tune the dizzies to the engines. A 240 supposedly would need a bit different curve than a 300 (sensibile I guess).
Hope this helps a little.
later.....
