This is a photo comparing front bumper brackets for a Challenger. The left is a '70 and the right is off of a '73. I believe the 70-72 and 73-74 brackets are interchangeable. Clearly the '70 bracket is shorter and the bumper mounts are different to accommodate for the larger bumperettes found on the '73-'74.
Regarding the weight, not sure how much difference there would be between the brackets. Perhaps a pound or two. I would think bare bumpers regardless of years would be nearly the same. The only other thing you may consider is to swiss-cheese the brackets to reduce some of the weight. You can eliminate the reinforcement plate located behind the bumper too.
I wonder... and by the pics it would seem that if there was a small difference, it would be mainly in the extra length, and that the same thing chopped down to 70 size might not weigh much more at all.
Okay... so i'm up on brackets. If i cant find earlier ones i'll just hack mine. They're rough anyways.
On the bumpers... are we
absolutely certain the 72 bumpers are exactly the same as 70-71? Not even a little plate behind them? I've heard conflicting reports over the years. I dont care about slots.
