I have a 74 and about a 2 years ago I replaced the 4bl carb with the Holley Sniper. With the original tanks we tried to bung them together in order to use one in-line exterior fuel pump. It didn’t work. Then I bought the Holley 534-38 dual fuel kit made for this application. I pulled all the lines apart and plumbed per the diagram using, now 2, external fuel pumps. The distributor valve was placed under bronco and all wiring was done per the diagram. With gas caps on, selector switch toggled to rear tank (confirmed by hearing the rear fuel pump cycle on when key was turned), the bronco started right up. I let it idle for about 5 minutes, then gas started spewing out of the FRONT gas tank cap. Crawled under and seems like the rear tank is bone dry and the front is full. I have double checked the plumbing lines and about to get under and check electrical. I’m so lost. Why would the rear pump/tank be engaged electrically and run, but the return seems to be filling up the front. Any help you could provide is very much approached. Thank you.