I had two Plymouth 225 slant 6 engines...put around 250,000 miles on them and the engines still ran good. The rest of the car died. Transmissions were good too. 1965 and 1967 Valiant and Belvedere. Single barrel carburetors...good gas mileage. Super easy to work on. Frequently putting ball joints on the front suspensions for those cars.
Had two Plymouths and a Dodge rot and fall apart around their 225 slant sixes. That torsion bar front suspension just wasn’t made for the pothole filled streets of Fun City in the 60s, 70s and 80s. The low distributor would sometimes fall afoul of the rinse in a car wash. (LOL)
A lot of cruising boats used them also. Not new, but as replacement engines. They could just hum along, day after day.