My memory really sucks and I'm not finding a good picture to reference.

I thought it was larger port was supply and smaller port was return.

See my picture below.

It's a 1974 CIS.

The top cover of the Bosch fuel distributor normally has directional arrows cast into it indicating inlet and return.
Good luck.

Ah ha! Time to get out my little mirror on a stick. Thanks!

No arrows, even looking at used units on eBay etc.

I think I may have my supply/return reversed, this is how it's plumbed currently. From what I can sort of tell on fuel diagrams, looks like the regulator is at the return hose side.

Anyone that can help confirm would be appreciated.

Hopefully this can help

Mind you Dan, my CIS on my 4 cylinder had markings of the “triangle”‘arrow cast into like this one. Not sure if it exists on your version. They do vary obviously.

Yes, learning they all vary a bit. I did have mine reversed. The fuel pump didn't sound right when pressured up and the "return" side didn't have any pressure. Swapped them around and let the pump run and things circ. Sounded normal.

The pressure reg on the distributor is the exit or return.

Lousy pic but maybe of some helpClick to view attachment