My 6.1 retrofit thread
The New Hemi with stock induction, flexplate, exhaust manifolds, and induction weights 485 pounds.
http://www.allpar.com/mopar/new-mopar-hemi.html
This is less than a slant six @ 525 Lbs.
This is also less than a LA/Magnum motor @550 Lbs.
And a LOT less than a GEN II Hemi a@750 Lbs.
If you combine a Gen III Hemi and an Alter-K-tion, you can take 150 Lbs off the front end of your car.
Of Course Rat is going to add a bit of weight with the turbos but it will still probably weight less than a fully dressed small block.
Regards,
Joe Dokes