The 727 is the only Mopar trans that will fit and be an easy bolt on and in.
After market companys can adapt other tranny's to your big block at a hefty price and some company out there (it escapes me now) has a OD trans for a big block.
I think your talking about the Keisler, its a gm trans with a special bellhousing to adapt to either the small or big block mopar depending on which one you need. I believe its a Gm 4L60E trans though. And sorry thats what I meant to say if your looking for cheap and stock your only option is the 727 but you can do the aftermarket od auto or I believe they make an adapter to bolt a gm trans to the big block mopar but I've only ever seen anyone do it with a powerglide for racing purposes so I don't know if its a very good option for a street car. Good Luck Justin