I can't tell where you live, and sure wouldn't be driving a car top down around here, but I Googled Jarvis out of curiosity and wonder if it wasn't just serviced by an outfit called Jarvis, in So. Cal...
I wouldn't be so quick to be apprehensive over something like an aftermarket transmission, anyway. Enjoy the car and find out about its history, and Jarvis' history.
An example -- I was initially happy with my new purchase -- in October. Since then, I am in the winter - cabin fever - mode and going through what I want in order to have the car straightened out for the shows in 2017. Nothing major -- I am just an owner / enthusiast, and not very mechanically inclined, but want to not worry about coolant issues, etc. So... as I dig around, I am beginning to find weird things that point to people monkeying around under the hood and changing things, probably in order to get the car to test well in its old home in California. Doesn't mean that it runs poorly, but it might have in the past. A car that is this much fun to drive would appreciate having poor functions repaired. So enjoy your new car, and congratulations!
So far I am wondering why I am the only one in the country that has a hose that has a reinforced "T" under the air conditioning components, and why the manuals don't reflect that. And... there is the driver's side front marker light with a goofy bulb socket that doesn't match the one on the other side... Then, the fact that there is not one chip on the hood paint. Car has 141,000 miles on it. Then there's the sport seat option listed under my console lid, but the seats aren't sport seats. I like the way my car ended up -- it looks nearly new. But... somebody monkeyed with it to keep it looking good, and I feel he was pretty resourceful doing it. I think you did okay! I get the impression that the more C4s we can get straightened out the better for the automotive community. I like mine.