If you have the cranks, and a matching BB or at least the spindle, give it a shot. Most bikes are fairly close to each other in terms of BB width and chainstay clearance.

Unfortunately, since the crank offset varies, just knowing the spindle length isn't enough. You could assemble the right crank onto the spindle with a cup, and start measuring where it'll end up, but by that time it's just as easy to install and see if it's OK. If not, you'll know how much longer or shorter a spindle you need.