Be careful when you take the stalks off the mounting plate. I don't remember which one - and maybe both - has little spring loaded copper rollers that make contact on contacts on the other side (I think that will make sense when you get into it). There are some detent balls too, if I remember. You'll obviously want to take it apart slowly and watch for things trying to escape. IIRC, that is the only real fiddly part of it. You should know that the thing that makes your stalks work for a Europa and not a Spitfire is the steel mounting plate so make sure you keep it (not that you'd loose something like that!).
Fiddly is NOT the word. The replacements are for a larger diameter column so...somehow you have to build the column up so that you can clamp it down tightly. First problem. I solved it with a couple rings of large adhesive heat shrink (I use it when I make high-power RF coax terminations on the end of heliax) which makes up most of the difference. I then carefully, with an extremely sharp bit, drilled a pilot hole 180 degrees from the clamp screw, and once the proper diameter was achieved with the heat shrink, and the clamp was tightened down fully, screwed a short stainless #6 sheet metal screw in so that the point pierced the heat shrink and bit into the column. It's tight.
Second problem...the quality of the ostensibly 'Lucas' replacement parts is questionable...I rang out all the leads and except for the horn button, everything was copacetic. Carefully disassembled the new rront plate (which has a different shape than the original... removed the stalk (yeah, there are a bunch of springs, wipers, one ball...I did it upside down in a tupperware container and caught everything), removed the offending stalk from both (the horn worked on the old switch plate...) and thank goodness the old stalk worked in the new switch housing...and the horn button worked, too...reassembled the new switch back end with the old plate (there is a screw hole for the column cover; the new front plate is a different shape, so there would have been no place to attach the cover...) Other issue is that the new turn cancel cam is deeper than the old...so, while reassembling, used the old nylon cam instead of the new one.
third issue: the plug at the end of the wire bundle for the switch is different. So...cut off the old molex (I don't have a pin removal tool for the large .092 pins...only the smaller .062...my bad...) with enough wire to splice onto the new wires. Soldered like colors to like color, shrink tube over the splice, and tested before wrapping with loom tape. Everything works as it should.
Put it all together on the column (with the lock screw...), plugged everything in, reattached the ground on the battery...turned the key...can flash the lights, hi/lo beam, turn sigs, horn, wipers, squirters...
Now, to finish with the leatherette cover for the column cover and put it all back with the OEM steering wheel.
I would hate to think about how much it would have cost to have someone do it for me. Lots of fiddling, fitting, and thinking outside the box...
