If the motor is basically stock, you could use a rebuilt factory 12” unit, like what would have come behind muscle car era 440’s.
If there are some hot rod items involved, particularly a performance cam........ something like a factory high stall 11” might be preferred.
Some of that choice comes down to personal preferences. And to make your life easier get the weighted flexplate that will open up your convertor choices.  B&M 10237 flexplate is what you need if you have a cast crank 440.
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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