carb problems

I have a 1979 Dodge half-ton 4 wheel drive pickup with an automatic transmission, a 360 CID engine and a thermoquad carburetor (No. 9225). I bought a used carb and put it on and it won't idle. I rebuilt the carb and reinstalled it and it still won't idle. I've tried backing out the idle adjusting screws one turn at a time. That didn't work. I checked all my vacuum hoses. Throttle body isn't cracked or broken. I increased idle speed and that didn't work. How do I get it to idle? Thank you.