Great idea! Thanks for your help!
I’m not home for the next few days but I will weigh them when I get home. In the meantime, here is a link to the original article in hot rod magazine. Picture 3 of 10 explains the 3lb difference and you can clearly see the contoured back and extra material that is removed compared to the a-body spindle. Bill Reilly from Reilly Motorsport is the author.
Swapping Disc-Brake Spindles - Mopar Muscle Magazine
