Yes, an ordinary upper sprocket with a couple extra tiny holes drilled so that the index pin sticking out of the cam will go into the sprocket in either the correct location, or two other locations wherever the bolts for the sprocket line up with the bolt holes in the cam. It just happens that the teeth are moved a couple of degrees different with each location. After milling a head the timing will be so screwed you have to "jump" the chain a tooth for nine degrees adjustment, then my little trick fine tunes a couple more degrees of adjustment. Well, it sure worked slick on Speedway GT, anyhow. I am amazed at how much difference four degrees cam timing makes.
Basically, the message in all of this is, when building a modified engine, even just putting in a different cam, timing marks should not be taken literally. You MUST properly degree-in your timing.