the trunk panels sort of fit. The trunk lid cover will not since the updated version has holes for the clips. Plus the side panels have a special mount so it fits but its not the best.

The seats will fit but the seatbelts will not sit correctly and you cannot use the later rear seat belts since they do not mount the same. The C pillar covers in my car are complete crap and I need to replace them but every time I try to carefully remove a C pillar I break a clip. Later w124 C pillars have the belt coming out perpendicular to the ground so I think there are two mount points for it, I need to investigate.

The front seats will swap over, just swap the bottom and backs to the original seat track, it will require rewiring if you have memory for the front seats. I need to do that for my drivers side. I'm still rocking the crappy leather back on a pristine tex bottom because I havent gotten around to fixing the wiring to work.