Actually the Lindberg model depicts an early war first series Elco 80' PT; so the .50 cal gun tubs are at the correct angle. On the mid war class, the forward gun tub was moved aft about 3 feet. The Italeri kit is a late war series Elco 80', the gun tubs were angled forward slightly.
The drawings below are from PT Boats, Inc.
PT 103, early war series, 1942.
PT 314, mid war series, 1943. The forward .50 cal tub has been moved aft about 3 feet.
PT 486, late war series, 1944. The .50 cal gun tubs have been angled forward.