I've thought about it many times and have yet to find any sort of pattern to the new numbers assigned in 1953, other than directional parity (68 is the only exception?).
14: new, maybe not immediate
15: 6A
16: unused?
20: 3 (part)
53: 5N
57: S24 (part)
58: 25A
59: 22
60: legislated 1953
61: S3 Spur?
62: S6
63: S1
64: 31A
65: 25B
66: 33-35 Conn
67: S1A
68: S39
69: 30
70: 40
71: 4N
72: S40
73: S41
74: not proposed until 1962?
75: not proposed until 1967?
76: new, maybe not immediate (renumbered 81 in 1964)
77: 46
78: unused? why? Interstate numbering had not yet been defined
79: 4A
80: unused?
81: unused until 1964?
82: S24
83: 49 (part)
84: already in use
85: not proposed until 1965?
86: unused?
87: S56
88: 35 (part)
89: unused?
90: not proposed until 1965?
91: 26A
92: not proposed until when?
93: S5
94: 8 (part), 31 (part)
73: renumbered to match PA 73