The US standard used to be 10 years after obscolecense, but I don't know for models, or other nations. If Marklin has an ICE 1 in the current or recent program, a floor pan from those should fit, unless it's not the motor wagon with the classic motor. That may be a problem. Perhaps you might locate a similar model used for parts, or use yours as parts.

Interesting idea. In my case it’s just one of the passenger cars. Not the loco. So the drivetrain isn’t a concern. But if that worked would then Märklin service dept not have offered that part up? The parts themselves are not listed spares and required a Marklin repair to fix so i would have to buy a used passenger car. I think I can glue it up again and will try that, was more curious about how short the parts inventory is available. Short it seems.

Oh, by all means, I get what you mean Rocca. Yet Marklin is not alone in this. Planned obsolescence has been in every manufacturing entity since the iron age. If everything could be repaired or updated indefinitely, we'd never buy new. For many, vintage is best. Others want the cutting edge in detail, tech., and style.
With classic autos for example, some n.o.s. parts are still available. When they are not, and salvage supplies have vanished, often a small custom order shop makes new parts. These are very costly to buy and make. For metals, there are repair techniques in soldering, brazing, or filling with fiber compounds. For porcelain and plastic there are clays, and modeling fillers like Milliput from the UK. It comes to how talented or patient one is in restoring.
In one instance with the first issue Marklin Seetal crocodile, one such maker offers replacement frames, as this model is plagued with Zinc pest. It was not the design, but poor quality control due to budget constraints by then owner Knigsbridge capital. New management offered no warranty. Another is the Trostberg Koff. I have both. The Koff has seized up. The Seetal has a dislodged nose resulting in a card an shaft from staying in. I see no breaks, but can not reattach it.