I think you did pretty good. Take 1000 pounds off that car and its in the 10's easily without much gear or compression. Pretty impressive.
Cam in my little 360 is 260@50 as well and its just a touch over 10 to 1 itself. At over 500 inches hard to believe your cam is " too big"
How do you launch the car and what rpm is it crossing the stripe at?

69 Dart GTS A4 Silver All steel, flat factory hood, 3360race weight
418 BPE factory replacement headed stroker, 565 lift solid cam
Best so far, 10.40 @127 1/4
1.41 best 60 foot
6.60 at 103.90 1/8