For reference.. I weighed my bare 5.4L block w/main caps. It was 215lbs and the head assemblies are 35lbs each. The crank is about 40lbs & the cams w/chains are about 10ish each. so 215+35+35+40+10+10 = 345 for the basic and heavy parts of a late model OHC V8.
I'd be supprised if a 4.0L weighs more than that!