I've never driven a W123 but I own a W114 250CE in the UK. You can really throw that car around in town. It's like a giant mini in that respect (the original mini, i have not driven the new ones). I'm not sure how well they handle at high speed but I have taken my 250CE to 115mph and it was rock solid. This was in the mid 90's and my other car was an 89 BMW 318i which did not feel as chuckable.

At the limit, you should expect any car with with IRS to be more predictable then a pickup with a solid beam rear axle because of unsprung weight. Pickup trucks have big engines and big axles and turning them too quickly would be like trying to spin a dumbell with your wrist too quickly, Force takes over.

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With best regards

Al