The forward pattern manual valve body has been recalibrated to ensure constant pressure, quick shift response and provides engine braking.
I watched that vid and have a problem with the B&M guy talking about the "300M Rockwell hardness input shaft".. Um obviously 300m is a steel alloy, not a hardness number. Also the vid shows the trans has a splined output for a slip yoke, definitely want a fixed output yoke. So I have my doubts about that alleged TT trans. Any good shop can build a 400 with the reid case and good shafts and billet drums for that $6k number.