Josh,
Here is how mine are made. First of all, they were made by a fellow inliner and installed by him. He is local to me. At the time there was a bunch of work being done with the dyno engines and he offered to help out.
There is a special plug that has a thru bolt to thread into a nut welded into the divider. The divider sandwiches the head with the bolt and plug.
The engine ran much better once the lumps were put in. Smoother idle and cleaner acceleration.
Notice the lack of lumps and the enlargement of the port. The intake manifold also had to be opened up to match.
