Not sure I understand your question. SST is one company that sells kits, as do Modern Driveline and American Powertrain. Each has their own tweaks, American Powertrain has their own shifters and such, and Modern Driveline has the ToddRon crossmember. One includes (or used too) the driveshaft, SST has the option for an aluminum bellhousing instead of the $1000 QuickTime bell. Each is different.
The ToddRon crossmember is only sold by Modern Driveline and was developed by ToddRon. But it is only a part of the kit that Modern Driveline sells.