If it was me, I'd cut the valley plate off the Barton manifold and just use the Indy plate. That way you could switch back and forth no problem. You may have to mill the bottom of the intake flange a little.
The Barton manifold would still work w/ non-Indy heads and the Indy valley plate.
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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