Are you meaning the holes? Duke Fox was never one to "follow the crowd", but he, also, was never one to be consistent from one engine design to another. Just did things different and that was the way it was going to be on that engine. A good example is the Fox 40. They make an iron piston version of the plain bearing engine, but offer an iron piston and ABC version of the ball bearing engine. Both Lew Woolard and I tried to get them to offer the ABC in the plain bearing version, but they wouldn't. The response I got was "they tried it once and it didn't work." However, the people who tried it were no longer with the company and they couldn't tell me why it wouldn't work. Now Lew has been retrofitting them and they do work, but that is another story. You won't get them that way from the factory.
On your 35 question, the two holes in the spray bar are to go sideways on the theory that the flat needle will first open one side, and then the other. And there "might" be a little more draw with the hole to the side (which you can, also, do with a standard venturi). So, you want to mount these with the holes straight sideways. On some of them you will find the holes just slightly angled to one side and that side should be faced down so you can't see either hole when you look into the venturi. Confused? I am. Now, on changing needles to another type, if the hole in the venturi is smaller as it might be for the smaller engine, or if the diameter is different (smaller?) you will get a difference in fuel draw. Whenever you change needle types you need to make sure the assembly has enough capacity for the engine and, also, to keep the same size body. If you go to a larger body (such as a ST type) you can compensate by either opening up the bore of the venturi or filing the new wider body to the same width as the needle assembly you replaced.