The difference in the spindle center distance (B-dimension in Sutherland's, between the outer peaks of bearing surfaces) between thin and thick cup types is 5 mm even. Difference between 68 and 70 mm spindles is 2 mm, pretty obviously. For instance, B-dimension of spindles for 68 mm BB are 49.5 and 54.5 for thick cup use and thin, respectively, while those for 70 mm BB are 51.5 and 56.5. Sugino (similar taper end size) spindles MW-68 were 51.5 and MW-70 were 53.5, and Stronglight was 56, TA 55 -- so you might get one of those to work depending on what you have in hand. The B-dimension doesn't tell everything, since the geometry of the bearing track is a bit different on all of these, I imagine; but it's a fairly good rough indicator of where the bearings are supposed to be in the whole configuration.