What will my 68 Dart 408 run in 1/4 mile?

Just drill a hole further back. Plenty or room and meat in that bracket.

That's kinda what I was thinking the more I've looked at it. One thing I need to check though is make sure my rear shackle won't be jammed back into the frame if I move the whole leaf spring back 3/4 of an inch. I gotta get it back on the ground so I can simulate how they are positioned when there's the weight of the car on them. If that looks good though I'll just be drilling the bracket and moving the whole springs back. If not I'll do the spring/shock perch and axle perch re-drill.