I've got both the Capris in my sig registered as classic and I live in the state of PA.
You must get the form (got mine from AAA)
Fill it out.
Take 4 pics of the car... front, back and both sides.
Car must appear as it would stock from the factory, including wheels. No aftermarket wing, ground effects, hoods allowed. They WILL reject you. Basically, if it wasn't offered as an option for that year, it can't be on there.
The car cannot be used for daily transportation and use is limited to driving it only once a week.
Send in the form and a check for $97.50 and keep your fingers crossed... they are VERY picky.
Once approved, the registration card is good for life.
You can carry any type of insurance on it that you want... I suggest a stated amount from State Farm. They will have you get an appriasal from a certified person and then insure it for that amount. That way, if you wreck it, you won't just get "book value".