Weren't these rated at 640HP (but they cut off the dyno run early so as not to scare the NASCAR guys, the curve was still rising). The benchmark. If you can't beat 640HP with your all custom $30,000 engine, then what exactly was the point?
Gotta have comparisons.
Cost of engine in real world, $25,000 FOB Larksville, Pennsylvania (570) 779-7843:
For substitutes, this place provided me with an excellent 390 longblock:
Thunderbird Ranch
It's all about what YOU want, build, buy, drive what makes you happy. My opinion.