The picture
@thebigredrocker posted for the VERTICAL banjo bolt is the 73-74 type, which DOES have a restrictor. The 75-78 HORIZONTAL banjo bolt does not have a restrictor.
SOOOOOO, if you want to try adding a restrictor into your return line, then you would need the earlier style bolt. Problem is, I've never tried to see if that bolt would fit in a 2F carb. It seems like a bandaid, and I don't advocate bandaids.
Fuel, like water, will take the path of least resistance. Logic says that if the hole in the needle and seat were insufficient, marginally increasing the size of that fitting would make it easier for the fuel to go INTO the carburetor than the return line, without the need to put a restriction in the return line.
That said, considering hundreds of thousands of engines and carburetors are out there running around without this modification, it is far more likely that the fuel delivery is inadequate, rather than the size of the opening in the seat.
I did open up a needle/seat assembly once, AFTER determining that fuel delivery was adequate. And it did solve the problem on that vehicle.
Cheers.