I have a old Trek 870 mountain bike ('89) with Shimano components and crankshaft. I've upgraded the components over the years but still have the same frame. I want to get a new frame and want to use my crankshaft, but would want a new bottom bracket. My question is if I get a new frame, will a BB that fits that frame work with my crankshaft or am I now having to buy all new. I just want to upgrade the frame as I like all the other items on my bike that I have upraded over the years (i.e. brakes, shifters, drivetrain, etc.). Don't want to spend $800 for a bike with low end components and start all over. I think the crankshaft is a square taper but I could be wrong since I know Shimano has their own style but I don't know if that came out after my bike.