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