sounds like you fugged up.
ok just kidding.
did you use the centering spring?
if so, are you sure you installed it right when you put the B&M in?
maybe you installed it with the B&M the wrong way, and when you put the stoker back in you put the spring on right.
maybe it was binding somehow with the B&M.
does it go into 2nd and 4th easily?
i know when i put the B&M in my car it hit the piece that bolts down ontop of the shifter ball.
i had to grind out part of it so the shifter would go back all the way to get 2nd, 4th, and reverse.