the 283 sender is normally right beside the thermostat gooseneck, just behind the oil fill tube - you may have the manifold style found on the 350 .... should work the same
the wire normally runs along the manifold side of the drivers valve cover, where there are a couple clips to hold it, shouldn't touch the maniflod, tho' I doubt that'd affect it anyway - I'd say the gauge is the problem, a 283 should show hotter than a 235, but still a bit below halfway
Bill