Help !! Running super rich.

I know it’s a truck.. but.....
I took the 2bb off of my 360 and put a low deck weiand single plane on it with a brand new Holley 600. Runs super rich. There’s no vacuum leaks? I’ve changed the intake gaskets 3 times. No leaks . I’ve put on 2 different brand new Holley 600 vs. also edelbrock 650 new to try. Starts to idle pretty high and runs super rich. Can’t find any leaks. New OE fuel pump. Runs horrid. Barely drivable. Runs a tad better with an old Holley 750dp VS on it. I’m at a loss. The plugs are immediately fouled. ? Ran great with the 2bbl. Just wanted a bit more pep I know. Single lane isn’t ideal. But it’s what I had. I’ve had all the nipples on carbs capped and hooked up to vacuum advance, pcv, and booster. All run exact same. I know it’s not the carburetors. There’s no change with them when I play with the idle screws. I lowered float levers. Adjusted choke. What else is there ? Thank you guys