Cannot locate the screw in type fuel filter

Good morning Roy,

My van saga continues. I have replaced the tank and sending unit. Cleaned all the lines to ensure no blockage. I have gas coming from the new mechanical fuel pump up to the carburetor, but the carburetor does not seem to get enough to run. I am wondering if I am losing pressure to the return line side of the new pump. I realize they did this in the past due to heated fuel line at the motor and to cool the gas back to tank to eliminate vapor lock. I hope that the selector valve being removed is not the culprit of too much returning and not enough up to the carburetor. Can it cap off the return port at the pump? Also after sitting for so long before I bought it, it may be possible that the jets are clogged with the dreaded green build up of ethanol gas. I own and restored a 1973 Mustang 351C and it sat for almost a year one time and I had to remove my new carburetor and clean the jets. Have not ran any ethanol gas in it since. I have seen a few post of adding gas to the bowl vent to get a vehicle to run and some have used this method to limp back home. Never tried this but it makes sense. Have you ever tried this? If I do and still have a running issue after this method, I think the carburetor may be the problem and a possible rebuild is in order. What is your opinion?