Yea, there has been a few threads across the interwebz about this, apparently Dart has been giving it some serious thought,whether anything will come of it, I don't know. Nevertheless, it would be nice to have a pre cast 396 and save myself the headache of machine work.
However, as you pointed out, to run fast with an LT1 most convert heads over and once you do that theres really no need to stay with the GenII block. I would think Dart would have better luck marketing a nice 355/383/396 line since most ported LT1/LT4 heads would flow enough to make them work well. Also prob have a bigger customer base of guys like me who don't want to deal with machine work etc.
And four digits are easy, forged 383, Ysi and some juice. Simple
