The ID should be almost identical. The 901's spring wire is thicker (which is what makes the higher spring rate, along with 1 less coil IIRC), so the OD is larger by about .080" or so. How much of the spring wire 'hangs out' past the edges of the retainers is one question....it could be perhaps in the neighborhood of as .040" if the spring stays centered on the retainer. That is around 15-20% of the wire diameter so most of the spring is still 'under' the retainer. So a bit of the spring wire hanging off of the edge is not a big deal IMHO as long at stays fairly well centered.
