A buddy had adapted a pair of Camaro Bilstein shocks to fit in his 73 Celica. He had to chopsaw off the bottoms to get them to work, and had spare metal lying around. Imagine a spool cut in half; the lip allowed the material to not fall through the hole that I had drilled, and didn't fill the hole with slag. We trimmed that puppy down a lot, and welded around the edge of it then ground that down almost flush with the rest of the manifold. If you stare at it, it looks like an anomoly from the factory.
