Selling rust free classic cars to be converted to electric is a good idea but should the seller sabotage the engine before releasing the car? And what about low mileage spare engines that have been saved over the years not attached to vehicles? A collection of x vehicles likely has 2x inventory of loose ICEs on hand - how best to permanently disable them? --
Don't. Someone out there may need parts off that engine even if the person formally buying the car has no need for it.
Unattached low mileage engines should be offered at premium prices, I'm guessing, since they won't be going into taxis or daily drivers to be flogged for years to come. Ideally from a carbon viewpoint they will be lightly used in collector cars/museum pieces. Awaiting a call from Jay's mechanic looking for a mint suz 1600cc that might see a few hours use per year. But one could over-think this. --