I have a January built 1972 K20 which still has the bearing.
For those who wish to keep the bearing in place the part # is MRC 209S. The only bearing I could find still had the 209 number but had a groove cut in the outside of the bearing for a retaining ring on another application, it did not interfere with my application and fit perfectly.
Here are the rest of the part numbers for the square O ring, 2 inner seals and t case to adapter seal (mandatory!! do not seal with RTV)
O ring : TK30046
Seals : 471424
T/C seal: TK10516, QU50450
from this thread
http://67-72chevytrucks.com/vboard/s...d.php?t=533389