Not sure about the Tangaloy but manufacturers regularly mixed tubesets to save money and hit a particular price target. It was fairly common practice to have CrMo main frames with hi-tensile or manganese alloy forks and stays on models that were upper entry level and lower mid-range. The only way to know for sure about the forks is via the catalogue or an original sticker on the forks. The only way to know for sure about the stays is via the catalogue.