Have the exact same thing in my dad's World hemi block. The cross studs are kind of a PITA. Threw away the fasteners they came with and had it align honed.

FWIW...the TTI headers on my cuda needed clearancing for the cross BOLTS in my KB block.

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