We do have a tech section of the forum and guess which is the first TSB?
http://www.348-409.com/forum/threads/63-t-10-front-bearing-retainer.27124/
http://www.348-409.com/forum/threads/63-t-10-front-bearing-retainer.27124/
The TSB that you posted suggests to change to a cast-iron retainer part number 604932We do have a tech section of the forum and guess which is the first TSB?
http://www.348-409.com/forum/threads/63-t-10-front-bearing-retainer.27124/
My 63 Borg and Warner transmission was a one year only, I also have a Muncie early 64 transmission where I can cross check the iron retainer bolt pattern. I am a numbers guy so I guess if I can find the Muncie 604932 cast iron retainer that should have the right diameter to fit the 553 bell housing and bolt pattern for my Borg and Warner that will be the part I want.I just checked this one to see if it fits a muncie case that I have setting around and the bolt pattern is not the same. Muncie has a larger bolt pattern.
I just remembered that I got a front bearing retainer from Cajun John, several years ago, that fit my T10 and the larger truck bell housing. I'm thinking he told me it was from a Saginaw transmission, but I'm not 100% sure.
The Muncie does have a larger front bearing retainer which fits the 553 bell housing but the bolt pattern isn’t the same as my 63 Borg and Warner which has a smaller front bearing retainer and to small for the 553 bell housing.If you notice in the picture I posted, you can see that the bolts are further inboard of the outer ring of the retainer on the B/W than your Muncie.
This is telling me that the Muncie has a larger front bearing than the B/W.