max,
thanx for your post, that's exactly what i did. i bought a cheaper shimano deore three ring crank set (i'm still hoping to find an original coda crank one day), took off the inside rings and cut off granny ring bosses with the hacksaw. then i mounted the 48t ring on the inside of the crank arm and used three spacers, but that pushed the crank arm too far out and there was no more thread left to screw it on to the frame safely. so i had to mount the chain ring on the outside using only two spacers. now the chainline is not perfect (it's out by, i think about the thickness of the chain) but it works somehow, so far. i also had to replace the chain retaining weel ( the coda chain ring had a very handy bash guard which shimano doesn't, if you know where to find an 48t size bash guard, let me know. i couldn't find it anywhere, it's mostly 44t these days). since i broke the coda crank arm in half i was able to see the way it was made and it's truly amazing, a proper aviation (if not space) technology stuff. i'm not really a downhill or offroad (or anything, for that matter) bike fanatic, i use this bike just to cycle around london (and you need an offroad bike for that, considering the state of london roads) but i do have an eye for beauty and i've chosen this bike for it's classic design, not for it's performance. but it rides well for what i use it for. i hope to keep it working for as long as i am able to ride it, i'll keep you posted. all the best.