Steele Rubber
It might be: 70-0219-73 (it is different from the side door seal)
"Weatherstrip, door edge. Constant section on some models. 5/8" X 5/8" size, high grade, fine grain sponge."
http://secure.steelerubber.com/gifs/70021973.gif

Jim Carter has one that supposedly fits. Call them for the dimensions (cross section). The picture looks OK. About 6 years ago I bought the rubber from JC and it was wrong. They might have the right seal now.

http://www.oldchevytrucks.com/cart/product.asp?prodid=DP136&i=|panel%20rear%20door||


Tim
1954Advance-Design.com
1954 3106 Carryall Suburban
1954 3104 5-window pickup w/Hydra-Matic
The 216 and early 235 engines are not "splash oilers" -- this is a splash oiler.