Thanks for the recommendations, all! I'd forgotten that Richard Polt's site also has these sort of manuals (I've used it many times for user and service manuals).
It's interesting to see some of the tips and techniques in some of these. E.g. I'd always centered things by doing some math on a scratch paper. House & Skurow suggest centering the typewriter, then backspacing for every 2 characters in the centered text - nice and simple.