The mounts will bolt right up to your 318.
The manifolds, however, may not- it depends on what year your "later year" 318 is. If it has the air injection holes below the exhaust ports, those need to be drilled, tapped and plugged. Anything approximately 1973 ish or later is going to have the extended exhaust pads below the ports for air injection, whether they are drilled for it or not. These will interfere with the fit of the driver's side manifold at the #7 exhaust port, requiring some grinding of the lower exhaust pad to get the manifold to fit flush. Go slow- test fit, grind a LITTLE, test fit again, repeat. Don't go hog wild here, you could break through. Don't grind the exhaust manifold either, it's a thin casting and you don't want it to crack later on. A nice thick exhaust gasket can help with the clearances here to minimize the amount of material you'll have to remove.
If your 318 is a pre '73 ish unit with smaller exhaust port pads, the manifolds bolt right on.
If your 318 is from a truck, you'll need to change to a passenger car oil pan, pickup tube, and dipstick.
You'll need the '66 and earlier V8 cable throttle pedal assembly, too.
And probably the V8 centerlink.