Warren on chassis type cars like pick ups and early US cars the front fenders,hood and radiator support can lifted off in one unit,this the Front Clip.
mercedes have never been constructed like this . The front fenders are bolted on to a frame which is part of the body and unless it's been bent,it cannot be removed easily.
What is being asked here is,Can I put the front of a W123 onto the unibody of a W114-115.
The easy answer is No,because a W123 is actually a narrower W116 with a heavier front chassis section .
A lot of Japanese tuner car parts are exported exjapan as "front clips " which are the fronts of cars are cut off from the windshield forward.
The experession "front clip" is often misused as a result.

This guy could do the same i guess gby cutting the entire front off and welding a W123 front clip on ,god only knows why though