Gas tank is mounted on three points, here are the front two mounts
The exhaust pipes are 1 3/4" OD, the common header pipe size. The problem with that is the actual exhaust port size on twin cam heads is 1 5/8". Usually there is an abrupt step where the heads meets the flange. I machined the flanges with the inside tapered to perfectly blend the two sizes. Also, they have a flat, perfectly matching taper on the outside of the flange, so there is no way the gasket material can squeeze into the exhaust flow. This happens often with aftermarket exhausts! These are machined from solid stainless steel on my manual lathe.
Here is the underside of the gas tank, with two giant mounts welded in. They are 1.5" OD flange, milled down where it goes through the tank. This distributes the load over a larger area of the floor of the tank (which is made from 1/8 chrome-moly flat stock).