Thanks to a very kind ANON, I’ve seen a full transcript of the letter (x)
Sam and Bobby-
Given what’s about to happen, I’ll be surprised if this package ever finds you. But if it does, I want you to both know that what I’m doing isn’t about giving up. John taught us better than that. This is about time. We’ve run out of it.
Left the Impala in Cicero. Where I’m going, we don’t need roads. I know you’ll look after her for me, Bobby- you’ve taken more for the team than anyone could ever ask. That makes you an honorary Winchester in my book.
Sam, you told me once that you pray every day not sure if that’s still true, probably isn’t, but if it is, give it one last try for me. And Sammy- one Winchester lost to this fight is enough.
Dean’s note, as best as I could transcribe it (05×18)
I am fucking sobbing why have I never seen this before