The shortcoming is in the w115 design, its trash and redoing it takes a long time and is a futile exercise in Pakistan where denter ustaad spits paan and says that he can redo the floorpan of it to “jenyan” condition with his oxyacetylene torch.
What he fails to understand is that all 3 layers of sheetmetal are corroded and causes massive amounts of flex in the body.
So keep the youtube excitement aside. And btw 2jz is now an obsolete ancient engine, much better options exist. E.g. the nissan vq35 or the toyota 2gr.