Not sure exactly, and no time to hunt it up tonight, but it should be very close to 600 pounds even, maybe a bit less.
Memory recalls an iron headed BBC at about 660lbs running. White metal heads should drop that at least 30 pounds a side, maybe more.
I THINK that 660 pounds MAY have even been with a factory iron manifold, and if that is the case, 550 to 570 pounds is very likely.
Back up on my pc, better search abilities.
Site I have shows a Mk-4 Chevy weighing 685 pounds fully assembled, factory. That would be iron heads and manifold most likely.
According to info from someone at World Products, weight dif Al to Iron on a BBC is 85 pounds, heads only.
I'm going to put up a guess of minimum 25 pounds dif. on the intake manifold. I still have my stock iron one, but my Performer RPM Air Gap is at my head porter, for eventual port match once the head work is done, so I cannot comparison weigh them.
That stock mother is HEAVY and the Ed. is a 1-hand breeze.
That has me guesstimating arround 575 pounds, PLUS accessory weight (alternator, exhausts, ignition, carb itself, fuel pump, etc).
Large aluminum valve covers and oil pans can actually be heavier than the thin sheet-steel stockers, due to sheer size and volume of material.
alum heads usually wiegh @70-80lbs lighter per pair than cast heads. easiest way to shave off 75lbs from a all cast motor is switch to alum heads. my bbc alum heads wiegh @40-45lbs a piece assembled.when i sold my 990's, they shipped at 78lbs each