The ornamental design for a truckheadlightshell, as shown and described.
FIG. 1 is a perspective view of a truck headlight shell.
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left view thereof;
FIG. 5 is a right view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The dashed or broken lines shown in the drawings depict portions of the truck headlight shell in which the design is embodied that form no part of the claimed design.