List from Inliner's site says 3835911 is 53-55 235.

http://www.inliners.org/casting/numbers.html

Freeze plugs for your truck should be in this parts catalog or perhaps a vendor could save you some time looking.

http://chevy.tocmp.com/1929_57chevyparts/index.htm

"Nothing astonishes men so much as common sense and plain dealing." - Ralph Waldo Emerson