Well I cked all 4 trucks and the frame rig (5th) and they all have the same holes that allow you access to the bolts that hold down some frame top plates/brake line clamps, and to get to the front motor perch hdrw on both sides, and the bump stop. And yes nice place for the mice to access the frame to build a home, the littel fuzzy chits.

In order of pics
1. L/H 79 ol red D44
2. R/H 79 ol red D44
3. R/H 79 ol red D44
(4) L/H silver 77.5 D44 (w/leaking steering box)
(5) R/H blue 78 D44
(6) R/H maroon parts truck D60
(7,8) L/H-R/H frame rig D60

FYI the cobbed up stuff (front spring perch drop, shock drop bracket and brake line BS) you see on the frame rig is thanks to the dumb a.. PO.