This is based on some mods I did whilst the coolant was out of my RV8 -
From earlier Wiki pages, you need to add a relay to the fan circuit, which isn't in the diagram supplied by Pilgrim. This is apparently because the transient current during fan start is more amps than the thermostat likes to carry, and can ruin the stat.
This is the circuit diagram -
..which translates into a standard four pin relay on the end of about 30cm of split tubing carrying five cables including the earth. The whole thing was attached to the chassis by a self tapper with the earth between the relay clip and the chassis. The relay and its base came from Vehicle Wiring Products, type R30A. You put the right sort of connectors (m/f) on the other ends of the cables, and wire it back into the system.
For the new thermostat, I went to an earlier page in this Wiki and found a long list of Intermotor type numbers. It says that for an RV8, you're best off with an 88/83 , as opposed to the 88/68 that I was supplied with by Pilgrim some years ago. Down at Eurocarparts the man knew about Intermotor but didn't stock their stuff. He went into his catalogues and came up with part number FAE 37810. It's made by some pattern part manufacturer and fits lots of Citroen, Peugeot and Alfa types, and it's also known as 126416, 60533503, 91516467, 95630939 .
It's three pin, and you need to know that if you hold up the stat and put the crossbar at the top the 88/83 bit is top and right.
That's it, mod done. There's a satisfying click as the fan relay switches, and the fans don't stay on for ages after the engine has stopped.