I have an 8 mm fuel line from Tangerine with the end beads and 40IDA Weber carbs. For some reason the fuel connector doesn't list the size on websites. What is an appropriate rubber fuel line size to connect to the 8mm line and the webers? If I need two different sizes that is fine.

I've seen people mention using American standard system fuel lines, on these metric parts?

5/16" (7.9mm) hose is available at your FLAPS.
That should be the same as the fittings on your IDFs.