I would think a 650 horse deal wouldnt be out of the realm of possibility with well done W2 heads and the associated goodies( roller, compression, etc) Not sure what a big block could make....
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