1970 Dart 340 Swinger trans swap American Powertrain or Silver Sport Transmission?
Neither the American Powertrain or Silver Sport 6 speed kits include everything you truly need.
American Powertrain has the crossmember that was originally made by ToddRonn restorations, which is by far the best for those keeping their torsion bars. But it looks like they're only selling the bottom half, which is bullshit. The tunnel work needed for a T56 is substantial and you need a significant upper crossmember to retain the strength in the chassis.
The aluminum bell housings out there now are nice, but, they're much thicker than the Quicktime bell housing and require more tunnel work.
This is my list for my T56 conversion from a few years back. I'm sure some of these links are probably dead but the part description/part number may help
My installation of the T56 in my '74 Duster is here, it's a lot of work. A 5 speed would require less tunnel modification, but realistically you're still going to need everything on that list. The parts themselves may be a little different for a TKX, but you'd still need an answer for each of those parts. If you have a 4 speed in there now you can have the flywheel resurfaced, you might be able to reuse the pressure plate (check the clearance because the input shaft is thicker on the T56, and check the slave cylinder clearance). I used a C5 hydraulic clutch set up because it's easier to deal with and MUCH less expensive than what either AP or SST will sell you and it's off the shelf. The one I linked is a "fancy" one from RAM but it's literally the same part as a GM one so don't bother with RAM. Some of the lines/adaptors are for a remote bleeder, but you absolutely want that especially with a Quicktime bell.
My "new" '74 Duster- or why I need a project like a hole in the head