Welcome to the forum.
Yes we have lots of opinions for sure. It is your car and you should do what you want with it. Just so that you understand why people say not to do some things will share some info.
I am not sure that in 71 you could even get the side stripe on a vert. In 72 & 73 you could but had to have the Decor Group which added the black or argent lower body color. Eliminated the rocker molding and you had a tail light panel that was textured metal. You also got the Mach 1 grill with the Decor Group.
No year of convertible ever got the spoiler. So when a purest sees one we cringe because it looks out of place and incorrect.
The only model that got the front spoiler was the Boss 351 but they look correct on all models so you see lots of them.
The rear spoiler was on one car I bought that I am eliminating now. He butchered the reinforcement inside the trunk because the studs fall in a bad place since it was not designed for a spoiler. You will also have to locate a set of two torsion bars for the trunk to stay open. The convertible is different from the Mach 1 and you will need to locate a Cougar convertible set of rods. The trunk will not stay open with an original type spoiler. What you ordered might be one of the light plastic spoilers and work.
You say you ordered an interior. If your interior code is CW for Comfort Weave White. The repo covers will not be even close to the originals. They will be embossed and not woven.
When you pull the interior out be on the look out for your build sheet. Can be stuffed in a seat bottom, under carpet or even under the sound deadening.
If when you pull the carpet out there is rust in the front floor you have a cowl leak allowing water to run into the floor, not easy to fix.
On the AC. You will need to replace all the O-Rings in the system with the new green type so it will hold the new refrigerant unless you stay with R-12. You will need a new filter dryer that is attached to the LF of the condenser. You should have the entire system flushed by a shop that can do a good job and put all new oil in the compressor. The under dash part of the AC is not easy to remove. You do have to take the dash loose and mover out of the way. For sure replace the heater core while the AC / heater box is out. Test the new core before installing they do have leaks from the factory.
For about any of your projects you can do a search of the Forum and find an answer.
I have 5 verts in various conditions from parts cars to original 48,000 mile driver.
If you order the cheap Marti report for $18.00 will give you info on how your car came from factory. The Sport wheel covers you have a very difficult to find nice ones. When you go to get tires be sure to point out to them that they are wheel covers not mag wheels. Many have the fake lugs twisted off or mangled because they thought they were real wheels not covers.
You mentioned PB and that is not as easy as you might thing either. Search the Forum for details.
You have to be tough on your projects on the car they tend to snowball and grow bigger.
Again your car but take a look at pics of verts with rear spoiler and without. Also the side stripes can be removed easily enough but you would need to do the Decor Group add to look original. See there is the snowball.
Here is a picture of a Decor Group like could have had side stripes but did not come with. It is a 73 which is different on the chrome on the front fender next to bumper.
