https://www.stuttcars.com/porsche-911-sc-g-series-1978-1983/
US models in general had an additional reinforment plate on the passengers side of the frunk to increase protection in case of a front crash. They were welded in manually in the factory. On drivers side in the frunk is the battery which works as a reinforcement by itself. Also the bigger rear bumpers were added and the ride height was higher than ROW spec to fulfill US crash regulations as the ROW bumpers were too low due to the ROW ride height. Also the bumpers were equipped with shocks/dampers. ROW models had simple steel tubes instead to be replaced after a crash. The dampers were the reason why the side bellow bumpers were introduced. Cabrios and Targas had additional reinforcements in the ground plate and in the A and B pillars. Therefore these cars require other floor mats. Compared to modern standards are the G body cars pretty soft and not very crash proof. Compared to the era of cars they're pretty solid and advanced developed in crumple zones. Both cab & targa bodies are winding when going over bumps. They're not as stiff as modern cars. This you have to take in concern. Also stiffer shocks made that situation even worsier. Bilstein shocks were a factory option for a more sportier/more firm handling. It's highly recommended to use the bilstein series option in maximum on a cab/targa. But many owners added the way more stiffer Bilstein sporty street suspension, which is by far the hardest/stiffest suspension available for 911's. It's way harder than many race suspensions from Bilstein and others. The body suffers on them very much. Best suspension for a cab/targa is stock suspension from Boge/Sachs.
The Targas were the result of US crash regulations as they had the roll over bar and a fixed rear window. They have been advertised as "security cabriolet" in the 70ies. That's where the name "Targa" is coming from which means "shield" in italian. Also US models had door reinforments to increase side impact protection. Later they were standard on all G body cars. Don't forget: In the end it's fairly old construction with roots in the 60ies...smoothly enhanced over the decades. But still not a modern car. If you're seeking for more security then a 964 might be a better (and unfortunately far more expensive) option...they had 70% of the car reconstructed and new designed, modern coil over suspensions, ABS and airbags.
In general the targas are louder than the cabriolets from wind noise. This is caused by worn rubber sealings and the fact that the roll bar is standing in the wind and the surface of the cabrio roof is more even.
PCA and others provided some quite good videos about the 911:
https://www.youtube.com/watch?v=EPo5Pv5og9g
https://www.youtube.com/watch?v=isCMSo-PHYk
https://www.youtube.com/watch?v=iYHx1imG2Lc
https://youtu.be/wnrFolQLR4k?si=52YeNpLt4JpdxVyv
https://www.youtube.com/watch?v=fZlLro_avJk&list=PLR0VqbBaNjTO6xehEZCJIwaVFAZzEtRRj
and many more. Many things are valid for both 911 SC and Carrera. The main differences concern the drivetrain.
This is one of my favourite videos about Porsches in YT, some young canadians bought three aircooled 911's and driving them home to Kitchener, Ontario.
https://www.youtube.com/watch?v=28hl_7zojy0
So years ago there was not too much hazzle to import these cars afaics...don't know how's today...
Thomas