I take it you don't have a Haynes manual for it then Tom? There are diagrams in there explaining the difference between the live axle and multilink axle.
This picture says it all though, multilink on the left, live axle on the right :
This one shows how the live axle is located in the car :
Out of interest, what oil did you put in the diff when you changed the diff oil?
You've found your dream home then?
That means it's a B200E then which puts it later than i thought. The very early cars had the dizzy mounted on the side of the block at the front of the engine. Also means the timing is non-adjustable.
From the way you've described the behaviour of that "ticking" noise, it sounds like a loose/cracked exhaust manifold or possibly a duff exhaust manifold to head gasket, or some similar exhaust blow.
The tappets need adjusting every once in a while, given that it's low mileage, there's a fair chance they've never been done so might be worth checking the valve clearances. Unusual for a redblock to need frequent tappet adjustment though.
The battery should be an 027 which is quite small, especially given the size of the car. There should be a battery retaining plate and a long bolt with a loop on the top end - a screwdriver blade is put through the loop and it is tightened that way.
An electric cooling fan will definitely reduce load on your engine and there are no kits available. Most aftermarket fans fix to the radiator using a sort of cable tie - bit tricky to explain so have a look at this ebay listing :
https://www.ebay.co.uk/itm/UNIVERSAL...S/351184375919
As for the switch, you'll have to get a coolant hose adaptor and a switch and wire that in separately - i can find more details for you once you decide to do it.