1969 Chevelle 540 Garage Build

[69chevelle540]

Ok so I was able to get the car moving under its own power this weekend and ive come across an issue. The motor has pressure, has good fuel pressure, ive checked the float level in the carb, and it is idling funky. when i take the belt off it fires right up and runs strong. put the belt back on and its slow starting and does a really weird progressive idle sound that i cant really describe so ive put a short video below of it in the driveway. You can here it about every 3-4 seconds and last a few seconds. ive been told to check the tightness of the pulleys, ive been told to check the MSD is getting good power, ive been told the carb could be gunked up due to sitting for over a year. If it was carb related i would think it wouldnt run well even if i took off the belt but it runs good without it. i have not checked the pullys and how tight they are.... would this be a common issue? im wondering if its timing, but again if fires right up without the belts. any thoughts??