4 speed auto transmission

Few options for ya

Keisler's "kit" bolts a 4l60e and includes all the parts necessary to swap. $4000-$5000 bucks, said to be no tunnel mods. Electronically controlled trans, lots of adjustments possible and lots of parts come in their kit

Gear Vendors O/D replaces the tailshaft of your current 727. $2500ish and shortened driveshaft and some tunnel massaging required. Havent seen a real world example in an Abody. But these are bullet proof apparently

A518....heard good stuff about SMR trans for this swap. Probably the most metal massaging of the three. I talked to them about a trans couple years ago and it was $3K plus. You can do the junkyard crawl for these trans as well. O/D can be controlled by a toggle switch. Moparts has a couple good threads about this conversion.