I suspect the converter is the culprit. You have a heavy car w/ a large volume intake, a big set of heads, and relatively small cubic inches. I'm guessing it's around 438 cubic inches? Stock stroke crank? That motor wants to rev, like all hemis do, so it's gonna need a loose converter.  Where does your current converter flash to? 116 MPH is enough to go mid 11s, just need to get it to 60 foot.
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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