Max P":14nqg1z6 said:Grind off the outer RH cup flange and this will convert your UN71/2/3 into an adjustable BB that will work in this way.
http://house-of-yes.com/phil-wood-y-bottom-bracket/
For a 73 BB on a 68 shell just add a 2.5mm spacer behind the RH cup and screw in the LH cup fully home.