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Obeast,
Where are you located? (Most of us include that info under our avatars.) if it’s near a metropolitan US area, chances are that there’s a bike co-op there. Such co-ops typically have a pile of triple cranksets, as well as long-cage RD and triple FD, all for cheap. As stated previously, cartridge BB are readily available (less than $25) in all the lengths you might require. Plus, there’s usually expertise there as well as the necessary tools, and even more help here on this forum of very friendly folks to assist you in getting it together to run magnificently for many years and hills.
If you don’t have access to a co-op or similar, post in the ISO (“In Search Of”) sticky at the top of this forum, and I’ll bet you will have a wealth of options open up.
A warning: if you take your lovely Nishiki into most LBS, they will try to convince you that your bike is hopelessly obsolete and you should just buy something new from them. We are here to help you overcome such thoughts.