My first 2bbl to 4bbl swap.. scratching my head..

Buy you a good shop manual or down load one.
Sounds like the 2bbl might just need a good rebuild.
I would rebuild the 2bbl first and see if you can make it run better.

As for the 4bbl.
Find a used aluminum intake in the for sale section.
Remove the 2bbl intake.
If the 2bbl intake is factory there is two small about 3/16 dowel pins that need removed from the block or you will crack the new intake.
Clean everything real good and install the new intake.
If the car is an auto make sure the kickdown linkage is adjusted properly before you drive it or transmission damage can occur.
Most Holleys do not align properly with the mopar kick down or throttle linkage without the proper adapters.