Gas cap: The original mate to the top cap screwed onto a base flange. There was a slight gap at the base, not a fillet, and the diameter was closer to the cap size.
The 4 tubes of the sidepipes flared to the next larger size for the first 2", so that the primary pipes fit into them.
The (Talbot) bullet mirror didn't have a flared base.
The roll bar rear brace joined center of the hoop. It wasn't off to the side significantly.
The rest of your stuff looks pretty cool.
