The 401 may be a lot narrower (60 degree V6), and help to fit in the frame and around the steering box.
What does the tape measure tell you?

Different folks like both engines equally as much, which one do you like more?

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
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-