I don't have an exact weight/value for this question, but I seem to recall somewhere around 650 pounds when fully accessorized (meaning, with alternator, smog pump, starter motor, iron intake, iron heads, air cleaner to pan, etc.). They're not as heavy as some may believe them to be.
I know there is a Ford engine weight chart somewhere on the internet; perhaps someone else has a more exact answer.
go to mustangworks.com. they say 720 with alumlnum intake. I think I read 756 somewhere with cast/cast. I know i bought a cheap engine stand rated at 700 lbs and did not feel comfortable untill I removed the heads at 100 lbs each. mine is a 429 scj 4 bolt main.