Sounds like the best thing to do is go back to the JIS taper BB - the cranks fit that now so you just need to measure chainline and fit a longer JIS BB accordingly (take difference in mm between current chainline and 42mm ideal, double that figure and that's how much longer the BB axle needs to be - sorry if I'm teaching you to suck eggs there!).
Sounds like the best thing to do is go back to the JIS taper BB - the cranks fit that now so you just need to measure chainline and fit a longer JIS BB accordingly (take difference in mm between current chainline and 42mm ideal, double that figure and that's how much longer the BB axle needs to be - sorry if I'm teaching you to suck eggs there!).