Most likely P225/75R15
Yes. If the tires are short enough. Go to tirerack.com to check original tire size. Google a tire size calculator to find out what tires will have the proper diameter (miata.net).
caprice bolt pattern is 5x4.75
Yes it will bolt right up
Yes I have an 84 with 22' s and my tire size is 265/35R22. I have air shocks in da rear and lift blocks on da front. Steering wheel Turns about a 1/4 turn from full turn on both side
Can a 84 Chevy caprice classic fit on a 83 Chevy caprice classic
Around 3500-3700 lbs
Depends on which model, engine size, condition, options, your location, & mileage. You know all of this and I do not. Click the link and you can find the value there.
84-87 Buick Grand Nationals came with this size tire as standard, as did 4 cylinder Mustangs from 91-93 when equipped with the optional 15" 10 hole alloy wheels.
Yes
No.... You need to change the whole back tail piece
the 84 caprice classic does come with both right and left side mirrors
just because your is stock and the classic caprice grandparent car do you expect it's fire lol