LBA 216243
L = 1953
B = 216
A = Flint, MI engine plant
http://www.1954advance-design.com/chev-specs/1953-Chevrolet-t-and-c-ser.pdf

3/8" fan belt for 3100-3800
11/16" fan belt for 4000 and bigger trucks
http://chevy.oldcarmanualproject.com/chevyresto/53148.htm

A 1948 water pump would have a wider than 3/8" fan belt