Hi Mick. Have you Tried Repairing the old Fan Motors. ? We Have successfully Repaired a few.
( All Sticking Brushes or Worn out Brushes. )

The Last one was a bit of a waste of time as They Now run Continuously due to a Faulty Ecu.
and another one also had a faulty Thermostat causing the fans to run Almost instantly after the Shortest of runs.