Something doesn't jive. Those pics are a W114/115. A 114 with an M110 engine would just be a 280 (or a 280C if coupe). An S-class from '74 should be a W116, and they had a 116 280S, but not in 1974, and anyway those pics are not of a 116.

Anyway, whatever it is, if it's in good condition and you like it better than your 240, go ahead and bite.

Also, the "gasoline return canister" is probably a charcoal canister. It filters the vapor vented from the fuel tank, trapping the gas fumes while the car sits. The fumes get sucked back into the engine when you start it up again. Silly emission control stuff and not at all needed for proper functioning of the car.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 401,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 26,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.
99 Mazda Miata 183,xxx miles.