I think it's down to the bearings Joe. The TC uses one 6006 (30mm x 55mm x 13mm) and one 6206 (30mm x 62mm x16mm), whereas the Special uses two of the 6206's, the same for inner & outer. I think that mod came in around the time of the wider brake drums.
So if you had the same hub carrier & accommodated the extra 3mm on the TCS bearing by machining into the casting then there would be 3mm, 0.125" less gap to fill between bearings ?
Brian
ps - for some reason the part numbers are different in my book.
Bearings - TC inner, A074D 6001Z, TCS inner X036D 6017Z, TC & TCS Outer X036D 6017Z
Bearing Spacers - TC spacer X046D 0148Z, TCS spacer A074D 0215Z.
Looks like there's something screwy there, my parts book is an olde worlde dead tree version dated Sept. 1972 ?