Well I have finished the installation albeit a temporary one.
I wired the fan up using the red and black wires (still don't know what the green one does). Had a leak with the temperature sender in the top radiator hose and had to reinstall it but seems OK now. I blew the 15amp fuse as soon as the fan started. It seems that the 960 fan pulls a bit more juice than the Davies Crag one that the wiring is designed for. Looks like I'll have to redo all the wiring and get a bigger relay.
In any case I simply replaced the 15amp one with a 20amp and the fan runs as it should. Easy to get the setting right with the temperature gauge reading the same as before. Haven't taken it for a run yet and I'll be sure to take the old fan with me and some tools!
Here's a few photos:
The original 960 fan shroud:
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Cut along here:
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Overlap the cut sections to make it not so wide and trim for top radiator hose:
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A nice fit:
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Fan finally installed and wired up:
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Tomorrow I'll do a test run. By the way, thanks for the help Jay.