I had an Abarth exhaust system on my 142 back in the '70s and I currently have a Simons sport version of their exhaust system on my 142. The late '70s Abarth exhaust system appeared to have been constructed from recycled soup cans and was pretty much rust dust in less that 3 years of regular driving. My Simons system was installed in 2015 and is doing just fine, although the car is not a daily driver and does not get used in the winter.

The Simons system is heavy gauge steel (and relatively heavy) - definitely no soup can construction. It uses flow through absorption mufflers so no real place for moisture to accumulate which should reduce rust issues. It is slightly louder than the original Volvo exhaust system and does not have a resonator so it has a bit of drone at certain RPMs (which you normally can't hear on the highway because of the B20E racket). I have been thinking about trying to fit a resonator for around town driving.

The Abarth had a really nice exhaust tip. The Simons is just a pipe sticking out the back of the car - if that matters to you. The Simons comes as a complete kit which includes a replacement down pipe which you may or may not need.