I suppose having the carb reasonably level is a good idea...
But the critical part is the U-joint angles.
Here's a driveline setup tech tip with some good links.
http://www.stovebolt.com/techtips/driveline/setup/index.html

Likely you can have both a level carb (if it matters) and correct driveline angles, but no question about it I'd favor the correct driveline angles.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
---All pictures---
"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-