a 904 is a lot lighter than a 727, (I'm guessing 40 pounds) but an aluminum head/WPH and intake big block is maybe 90 pounds more than a comparable aluminum small block, I don't see 200 pounds combined though, maybe 140?
Pretty sure my 517 low deck is as light or lighter than an all aron 340.

I do know that Small block iron heads are typically 2 pounds heavier than a BB and possibly the intakes (iron or aluminum) are heavier as well. The iron Small block w/caps is about 60 pounds lighter (~165 vs 225 w/caps)