It's been a long, long time since I owned a 2.6 with a carb, but I'd proceed like this. Get a small hand pump and a 15psi pressure gauge. Identify the suction line by cycling the pump lever and see which line has suction.

Seal the pump to the pressure gauge with one of the two output hoses, and cycle the lever and see if the pressure stabilizes at around 7.5psi. That is the carb bowl feed and the other is the return.

Not responsible for advice not taken...