the front sheet metal was different on fx to fj but the subframes were basically identical in the pressings there are a few minor differences like the wiring hole for the horn on early fx but as for bolt holes for the guards the the same i've fitted a very early fx sub frame to my car as the original had rust bad the left inner rear leg has no hole for the speedo cable to go through also i notice the mounting holes on the subframes varied so most times they won't bolt up the same positions i helped restore a 54 fj which had that triangle you mentioned but had fj front A pillars probably a left over body that simply got later fj pillars the rear shock position varied on early to later fj utes and sedans i think holden just simple used whatever was avaliable at the times which varied from factory to factory so many odd things pop up on the early holdens the FE FC ute rear window is different to the FB EK utes the rear pillars are wider i was told they did this as a the FE FC utes had a cracking problem
