This chart compares the casting weight of standard and spey DTs to WCs and MSs at their respective lengths.
The chart is sorted by casting weight, grouping lines of comparable weights together. The "Two Over" rule of thumb works in pretty well most cases for both WC and MS length lines. As the WC and MS grain weights do not go up in a linear fashion (and the DTs do) we end up with the heavy weight MSs tending to be a bit closer to one over.
To use the chart, locate the WC or MS that works best on your rod and the DT lines closest to it would the best choice when fished at that length.
Here's the chart for Airflo lines: