tjm - just saw a ford/mustang publication on the mag stand yesterday (wish I could remember which one) that was chock full of the dimensional data on all Ford V-8's; it confirmed what I'd heard all along, that it's indeed heavier as well. Remember, it's a cast iron block now. The plain mod motor is a good 100 lbs. heavier than a 5.0L with aluminum heads. Go figure.
Hmmmm....What do the various Mod motors weigh anyways?
Ford 289/302 V8 460lbs (late 5.0s are a bit lighter)
Ford BOSS 302 500 lbs
Ford 351 Cleveland 550 lbs (includes BOSS)
Ford 351 Windsor 510 lbs
Ford Y block V8 625 lbs (272-312 CID)
Ford FE big block 650 lbs (332-428 CID)
Ford FE big block 670 lbs ('59 352 CID)
Ford 429/460 V8 640 lbs
Ford 289/302 V8 460lbs (late 5.0s are a bit lighter)
Ford BOSS 302 500 lbs
Ford 351 Cleveland 550 lbs (includes BOSS)
Ford 351 Windsor 510 lbs
Ford Y block V8 625 lbs (272-312 CID)
Ford FE big block 650 lbs (332-428 CID)
Ford FE big block 670 lbs ('59 352 CID)
Ford 429/460 V8 640 lbs
I'm operating from memory which is increasingly unreliable - but I believe they had similar data to yours in the article I saw - and if I'm remembering it correctly they had the cast iron 5.4L mod blown motor at 673 lbs., and the 4.6L aluminum mod motor in the 550-570 range. I'll head back to the magazine rack and see if I can put my hands on the issue. Someone else's data - can't say I've weighed them myself - but they also had ht/wt/length in inches for each engine too. It does make sense though - it's part of the reason that the new Stang's/Cobra's weights have ballooned into the 3500-3700 lb range, with no improvement in front to rear balance - still VERY nose heavy.