Does anyone make a fuel level indicator for the SU carbs that can be mounted where the drain screw goes, and be left in place permanently?

Sounds like you may just have invented one, Paul. Draw it up and let us kibbitz...

Nissan make[made] this:classic:

However it is a diagnostic tool, not intended to be left in situ.

The top of the tube needs to be open to the atmosphere or the fuel bowl vent to allow it to fill with fuel.

I've seen the old Nissan part, is that still available anywhere?

I guess a permanent mount isn't realistic, since it has to be vented on top. Unless there's a way to baffle the vent...... I'll break out the CAD program and the , and see what I can come up with.