Re my 26 Fordor which I am restoring to authenticity, I plan to use some existing Champion A25 plugs which were in the car and they have cleaned up beautifully.
Are these correct
Is the main body of the spark plug bare metal
I have seen some that have a black finish. If this is the case how do I refinish my existing plugs to have this black finish
What is the correct plug wire screw on the top. Is it brass.
Is it long and tubular like a straw or is it larger and more knurled
The original plugs for your car would have been Champion "X" if they were Champion brand plugs. Ford was using more than one brand of plugs. Champion would be the most common of course.
The Champion A25 marked plugs came in the 1950's or later.
I believe the black finish was what Ford called "Raven" finish. Some of the restoration services sellers offer a kit to do this finish.
I will leave the rest of your questions to others more knowledgeable than I.
Ron the Coilman
I'm not necessarily more knowledgeable than Royce, but I will add that you can get a bluing kit from a gun shop for about $10, which will blacken a lifetime supply of spark plug bases for your T's. They look very well with this finish.