Anybody break a stock block, if so at what hp?

My combination, is a yearly thick wall 340 .60 over 4" stroker(steel) crank 12.1 comp. B1ba heads (300cfm on intake at 700") custom cam motion with 1.6 rockers it is at 684in. 684ex. Edelbrock Str with a custom 1"spacer raising top plate and woodspacers under ea. of the two holley650 hp, billet main caps, studs, and gurdle. It dyno'd at 579 hp 580 tq at 5800rpm. I want to put a 200hp shot of nos on my 68 gts full interior all steel. I wish I would have been more patient for an R3 block. But wondering what you all think?