Not trying to insult or disrespect, but before thinking carburetor size is a problem.
1). Are you sure you installed the cam in the correct position?
2). Did you install the correct lifters for the cam (did not recycle the old solid lifters)?
3). Did you set valve lash with the cam in its correct position for each cylinder?
4). Am I reading you correctly?, one full plus a half turn is to much lifter pre-load?
5). Have you tested for vacuum leaks coming from under the intake manifold?
6). Have you checked fuel pressure?