Sorry to dredge up an old thread, but I'm having a similar issue with my 6400...the right front wheel cylinder I'm replacing has "5453781" on the casting, and after seeing Rustednuts' response on here, saying the casting number is 5453781, but the whole unit part number is 5453780, I'm still at a loss. Chevs of the 40s shows 5453780, but the brake line entry port is angled out on theirs, whereas mine comes straight out of the casting. Any advice?
Thanks!
