Looks like a really good car, congrats. They are getting so much less common on the market. The engine refresh and SSIs are a huge deal, they all need this and it's $$$$.
One thing, though. The cabriolet conversion was done by someone local in AZ., not the Porsche factory according to that paperwork. That second sticker was something that dealers slapped-on the window next to the Munroney, usually for their dealer mark-up and a few dealer installed accessories, as listed on yours.
I'm sure it was a good job and it looks like they used a factory top and frame, (what else would they use), I'm surprised they did not charge more. From a mechanical POV, it is not a difficult conversion. All factory cabs are just targa shells w/o the roll bar. The top of windshield bar was exactly the same, IiRC.
The tea tray spoiler was the optional rear spoiler from Porsche on the SC in those years. That switched to the smaller Carrera spoiler in '84 with the 3.2. I used to see a lot of grey market, ROW SCs at the dealer in the '80s with the "sport package" option which was spoilers F/R and sport shocks. The tea tray on this car was added by customer or dealer if it's not on the Munroney sticker.
I'd strongly suggest getting the 915 shifter and linkage working perfectly vs. putting any kind of quick/gate shifter on it. 915 transmissions are amazing but need to be shifted correctly, if you "beat the synchros" with the speed of your shifts, you'll be opening your wallet really wide.
