F = Flint plant
1 = January
16 = 16th day

The "J" suffix on 235 engine serial numbers appeared on 57',58' and 1959 Thriftmaster engines

57' - http://chevy.oldcarmanualproject.com/models/engine.htm (near the bottom of this page)
58' - http://chevy.oldcarmanualproject.com/chevyresto/58t074.htm
59' - http://chevy.oldcarmanualproject.com/chevyresto/59tsn03.htm

"Nothing astonishes men so much as common sense and plain dealing." - Ralph Waldo Emerson