According to my scanned
Sugino catalog, the AT takes an RB spindle with a BB-SC bottom bracket, and either a 3U-B (bolted) or 3U (nutted) with a Maxy.
The RB spindle looks like it only fits the BB-SC bottom bracket.
Dimensions:
129 mm overall
30.5 mm drive side
16 mm taper (I think this is the taper length. It's confusing, because on the diagram it looks like the non-drive side length, until you look closely and realized that it's measured from the start of the taper rather than from the spindle shoulder.)
78.5 mm R' (measured from the centerline of the BB to outside edge of the crankarm's mounting bolt hole.)
That catalog doesn't show a Maxy bottom bracket, so the 3U-B / 3U dimensions come from Sheldon's database:
124.5 mm overall
32 mm non-drive side
40.5 mm drive side
Symmetrical equivalent 133 mm
But then, in the crankset-specific section of the database, for the Sugino AT Saint Sheldon calls out both a 127.5 and a 122.5 Shimano cartridge BB as a replacement, both with a 2 mm drive-side spacer for a 150 mm tread, plus a 115.5 +2 for a 139 mm tread. I'd assume that which one you need will depend on your frame and chosen gearing. (Smaller rings can be run tighter to the frame, since the chainstay angles outward.)
Hope this is useful.
--Shannon
PS: Does Phil Wood still do custom spindles? I bet that they used to make a bunch of bottom brackets for Sugino ATs, maybe they'd make you one?