I've used the Chilton's Bmw Coupes and Sedans 1970-88 Repair manual for my coupe and M6 for quite awhile now. It's quite good for routine maintenance with good instructions but it's not coupe specific. It does contain a nice tune-up spec section though.
Try to locate these old publishings, these are probably not available new anymore. Bmw 2500, 2800,3.0, 3.3-1968-77 by Autobooks--covers both coupes and sedans. Also Haynes-BMW Sedans 2500, 2800, 3.0 & Bavaria--Sedan specific but since drivetrain parts are all the same, this is a good reference manual. I've used these two books since the late 1980's, they are both excellent and contain many pictures and diagrams in addition to very good 'how to' instructions.
Bert
72 3.5 CSi
88 M6