I was looking in the manual PDF for a page with all the keyboard controls, but the manual just gives you the controls piecemeal. Is there a quickref card somewhere?

Which one?

A keyboard reference was included with the original boxed release of the game, but isn't included in the GOG release for some reason. A copy of it is available on the Local Ditch Interstate '76 site (in the Downloads section; the forum won't let me "post any links at this moment", otherwise I'd link to it directly). I've attached the images of the reference sheet to this post for convenience.