Early e39's used aluminum front and rear calipers, might be possible to install them on your spindles with a little work. If you're going to that trouble it's probably smarter to go Willwood or other aftermarket race calipers just to open up the pad possibilities.
edit: Early e39 528i and e36 M3 actually share the same front brake pad, offset is likely buggered but at least the pad size is correct.