I installed a set of stainless lines from the tank for my /4 but decided to go with a /6 conversion with webers. How do you run the return back to the tank or should I at all? Is it as simple as plumbing to the first carb, then to the second and adding a different banjo fitting on the second carb then back down to the return line? Is one of these methods or another prefered?

Kev

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Mr Gasket (Mallory) made a fuel pressure regulator with return and multiple outlets (it's still in my desk somewhere).

Fuel pump .... regulator ... line to each carb (no return from carbs) ..... return from regulator to tank.

If I find it I will post an image.

I dead ended mine at the carbs. No apparent ill effects. Just make sure your line pressure NEVER goes over 4.5 PSI and your float seats are good.
I don't trust fuel pressure regulators.

I should have added I'm using a CB Performance rotary pump rated at 3 1/2 lbs.

No need for a return though the concept of fresh, cool fuel to the carbs is nice.

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ditto until mine became a 3.2 conversion.

Don't remove the old return line. You might need it eventually.