OK, in the 1950 Betty Crocker Picture cookbook, says guinea may be broiled, fried, braised, or roasted using same directions as chicken.
The Doubleday Complete Contemporary Cooking (Vol. 1) from 1975 says guinea has a "rather dry, delicately gamey meat" and are prepared like chicken. Roast, spit-roast, and braising are the recommended ways of cooking. 350F oven temp for 1.5 to 2.5 hours, brushing with butter or drippings.
Better Homes & Gardens 1967 "Favorite Ways with Chicken (Turkey, Duck, and Game Birds)" says roast covered @ 375F approx 1 hour unstuffed or 1-1/2 hours stuffed, uncover for last 20 minutes. Also has a recipe, "Guinea hens and Kraut" if interested
The Joy of Cooking (1962 printing) recommends for stuffings: cooked wild rice; bread dressing; or fruit dressing (glaze? may need to read more here). Also recommends dredging with flour then placing uncovered in a 450F oven, but reduce heat to 350f once bird is in, cook 30-45 minutes or until tender (depending on stuffed or unstuffed; and size) Basted or "barded" which is putting bacon over the breasts.
I have at least 2 more with instructions on guineas (maybe more?) and will edit this as I find them.