They may need a little machining to fit the standard English 1.375 x 24 BB shell and standard ISIS bearings?
My spindle preference has shifted from square taper to IsIs because for edirtbiking the ST spindles occasionally break …maybe from the cranks & shaft hitting rocks ?
SickBikeParts has the eBay seller’s name of brook45izy. They do have 2 sizes of Isis spindles for sale measuring 148mm & 153 mm. The price is good but they are too short for my motor width.