Give us a pic of the throttle and kickdown linkage.
A lot of times, after a carb/manifold swap has been done; the throttle and kickdown linkages can be suspect if the correct parts or modifications have not been done also- which can cause similar symptoms to what you describe. The kickdown linkage is especially critical, if it is improperly done or mis-adjusted, transmission damage can result.
The carb and manifold you have are good and will result in a decent driver when done right.