I'm with you monte...but by that same logic wouldn't the loss of 10-15 pounds on the front have a similar (though not identical)effect on the Front/rear weight distribution in terms of %F/R? Your adding rear bias (shifting the CG back) by taking any weight from the front of the existing CG.

E bodies and 71-Later B bodies TEND to be (even) more front weight biased than 70-earilers, I think the cowl area with the hideaway wipers, bigger windshields and longer overhangs have a lot to do with it. But E bodies are inherently worse (nose heavy) in terms of F/R because the rear overhang is so short. Just basing the "assumption" of moving a big blown Hemi back on an E body SHOULD help...but I get and understand your point. I also had a Blown BB in my 70 Charger and it was nose heavy as He!! too. so just a semi-edumactaed guess here...590's got a lot of Pics on Photobucket to give us an idea. The cal trac/monoleaf/spool is almost certainly lighter over the rear axle than stock F/R...

My Big block Duster (both B and RB) hooked much harder and felt like a different car when I got rid of the spool mounts and used an elephant ear to set the motor back a good 1 1/2" (to where the PS valve cover was nearly rubbing the firewall). so did removing the tank and putting a fuel cell in the rear tire trunk well. So...Just going from Gut from my personal experience on those types of cars.