Due to changes in emissions laws, carb idle solenoids were used on all '69 (M-code) 440-6bbls, all '70-'71 6bbl engines (including the 340 T/A-AAR packages), '70-'71 Hemi engines, and '70-'71 ...
Why do you suppose carburetors are so hard to adjust? Even a simple jet change requires major disassembly. It's my hunch they're made this way just so the average idiot can't screw them up. But ...