Wayne Euper from Richmond Mo built the BW T-10 for me from transmission and parts he had.
Wayne was the go to transmission builder for many years for a large number of cars - I think many guys on the forum knew Wayne..
He was a Chevrolet dealer transmission guy ( as I remember )
i drove my frame off restored California GM 1962 Impala 380 HP 409 with the Borg Warner about 500 miles ( that Wayne built for me) and it popped out of gear.
I shipped the transmission back to Wayne and he rebuilt it again ( I don’t remember what he did to the BW - it’s been too many years ). It still jumped out of gear with decelerating in 2nd gear. I ended up selling the car to build a new garage ( My 62 409 is now in Michigan sold for close to $ 75,000 in 2019 - I sold it in 2003 for half that value - it was a 993 point out of 1000 point 62 Late Great Chevy show in Springfield Mo) - it now has a Super T-10 in the car)
Wayne built at least 8 - BW and mostly Muncie 4 speeds for my 62 frame off restorations over a 15 year time frame, always had great 4 speeds that were and still are great ( I still have 2 of his Muncie 4 speeds in my 62 & 57.
i like how a Muncie 4 speed shifts ( smoother )as compared to a BW 4 speed
Paul