I have a 2003 Cobra DOHC (iron block) goint into my 67. I weighed it with all accessories including supercharger, alt, ps pump, ac pump, pulleys and belts, exhaust manifolds and flywheel with clutch/pressure plate. 700lbs. I have an aluminum block for it which will reduce weight by about 70lbs. At 630lbs or so it will be slightly less than a big block.
I weighed a complete 289 with all accessories (no ac, no ps, no exhaust, no clutch/pp but with starter) 485lbs.
The all aluminum 347 in my fastback with the same accessories as the 289 weighed 365lbs.