1981 was the last model year for non-turbo diesel W123's in the US market.
The US 300D would have been turbo, with EGR. The 300D turbo was intended for the US market only. All 300 non-turbo diesel was continued til the end for D and TD. Coupes, as mentioned, were ended for 1981 model year. (diesel coupes also only intended only for the US market, so any 300CD in euro form is a virtual unicorn, I have not yet had confirmation one exists)
The IP does vary between US and Euro non-turbos, but the Turbo 300TDs in Euro and US form is shared, at least in style. I doubt the Euro models are made beefier, but perhaps tuned different (without the EGR system to lag on it) in non-turbo form (emissions again) as the turbos were. The factory tuned settings were opened up closer to the Euro standards the last couple years of production.
Hope that helps
The US 300D would have been turbo, with EGR. The 300D turbo was intended for the US market only. All 300 non-turbo diesel was continued til the end for D and TD. Coupes, as mentioned, were ended for 1981 model year. (diesel coupes also only intended only for the US market, so any 300CD in euro form is a virtual unicorn, I have not yet had confirmation one exists)
The IP does vary between US and Euro non-turbos, but the Turbo 300TDs in Euro and US form is shared, at least in style. I doubt the Euro models are made beefier, but perhaps tuned different (without the EGR system to lag on it) in non-turbo form (emissions again) as the turbos were. The factory tuned settings were opened up closer to the Euro standards the last couple years of production.
Hope that helps
