On the face of it, the obvious choice would be to lay it to rest.
But there are items to consider:
Overall condition of the vehicle and how well it has been serviced over the years.
Mechanical condition IE. transmission, brake system, electrical system, suspension, front end etc.
If all things are mechanically sound it might be worth the cost of the repair/replacement of the engine compared to the expense of a new vehicle.
The basic idea would be invest the least to get the most out of it.