Just FWIW, there is a cut off from the earlier vettes where the tops don't interchange with the later models. I'm thinking '87 or '88 is when the mounting locations changed. Maybe someone else could verify the correct year when they changed.
I believe the OP is talking about the convertible hardtop (RPO CC2). This top was first available in 89 and the tosp are the same thru 1996. GM did have a retrofit kit to install the 'vert hardtop onto the 86-88 convertibles, but those kits are very hard to find now and thwy would have to come off donor cars.
The coupe targa tops did have differences in the locations of the encapsulated bolts in the windshield header. I believe there were 3 differents setups. 84-E86, L86 to 88, and 89-96.
As far as the price, I think it's a bit high unless the weatherstripping is like brand-new (check out the cost of replacement hardtop weatherstripping :eek ) and you get the tools, the decklid protector, and the top is already the same color as the car it's going on. If the top has to be re-painted to match, figure on $400-500 extra for that alone.
The hardtop defogger will only work if the proper climate control head is in the 92. Verts that did not get the factory hardtop ordered with the car got a slightly different A/C controller and the ground wire for the defogger was not installed on the car. (no biggie to add a ground wire). The 92 owner's manual has a section on how the hardtop defogger is turned on along with a pic of the correct button.
The defogger hot lead is on all the 'verts; it's an orange 12 gauge wire located under the carpet just in front of the forward soft top frame hinge on the passenger side. A ground wire can easily be screwed to the driver's side shoulder belt attaching tower.
Red Vette is right about where the tops were made. American Sunroof Company in Bowling Green had the GM contract to make them. The plant is only a couple miles from the Assembly Plant. Finished 'verts were delivered there so the tops could be installed and the door windows adjusted for both tops and then the cars were returned to the Assembly Plant for final finishing.