Old Shakey was the largest transport plane in that era, 4 engines, considerably larger than s Gooney Bird (C-47).
The key being "in that era." The C-54's fuselage was 95 feet, and the C-47 was 63 feet, a difference of approximately 32 feet.
The wingspan of the C-54 was 117 feet vs. the C-47's 95. A difference of approximately 22 feet.
So larger, yes, but not massively so. C-54 was much smaller than the Boeing 707.