66 barracuda
I would say the motor looks like a late 80's 318. It has the offset thermostat outlet and the valve covers are black. On the drivers side (I think) just above the starter is the casting date, either there or on the passenger side. A late 80's 318 is not a bad engine - since it already has the small chamber swirl port heads on it and has a hydraulic roller cam in it. Port the heads and throw a racier roller cam in it, flop a 4 bbl on top and you have a nice street cruiser.
To answer your question if it is a non magnum motor - all your 273 parts will bolt on, valve covers intake etc.
It looks like it has some of the correct stuff on it already.