You say the 77 was not spinning fast enough right off? On my old well worn 78 I have run into that issue a few times over the years. Don't get nearly that cold around here, but still my car has had some slow starts, or failures to start over the winter seasons.
I did two things to get the old diesel to turn over in the AM better. First was I replaced the short ground cable with a new and very heavy one. Scraped and cleaned the contact areas and then used electrical grease on them. After that and some improvement I finally just replaced the starter with a fresh rebuild and replaced the positive battery wire also. Gave it the same treatment where it seemed appropriate.
Has started fine ever since, except for a couple of battery failures. I blame that on a series of Exide batteries I had in there. Kept replacing them with warrenty batteries and they kept letting me down.