Koleno isn't making anything. I think your only option for a new block is either KB or Indy, but both in aluminum. That HP Performance place may also be making blocks still, but I think they're aluminum only also. You'll have to scrounge around and find someone selling an older MP, Koleno, or World cast iron block and probably pay more for it than they did when it was new. 
CHIP
'70 hemicuda, 575" Hemi, 727, Dana 60
'69 road runner, 440-6, 18 spline 4 speed, Dana 60
'71 Demon, 340, low gear 904, 8.75
'73 Chrysler New Yorker, 440, 727, 8.75
'90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt
'06 GMC 2500HD LBZ Duramax
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