You need a longer bb spindle due to Raleigh's longer (~71+mm) bb shell. An Italian-sized number 5 or a number 7 MTB spindle MAY work, but many are too big for the old Raleigh cups so it can be hit/or miss. Another option is Velo Orange's Grand Cru Cartridge bb but it's pricey (nothing like a Phil Wood bb though!).

Assuming you locate an JIS spindle you ought to opt for a JIS taper crank or your chainline will be messed up (cranks sitting too far out) so stay with a Japanese crank in that case. In my experience every crank is a little different though - so it could still be wrong, with worn square tapers sitting too far inboard.

Frankly, is is a LOT LESS FRUSTRATING/EXPENSIVE to stick with your lovely chromed-cottered crank. The weight difference is of little real consequence unless you are a weight weenie (in which case you would not be riding a GP).