Welcome to Hotrodders.
The most common thing that gets glossed over during a transplant like you did is the TV cable installation and adjustment. There are several threads here and on other boards addressing the TV cable in detail. Do a search on this board for 700R4, TV cable, etc.
Also do a google search of the internet for the same words.
With all that said, yes you may have a problem with the 2BBL carb if the TV cable connection point isn't in the correct relationship to the throttle shaft and adjusted correctly.
Give us some more details of the problem if you can. It would be my guess that 3-4 clutch is burnt. What is the condition of the fluid?