For that, you'll need a good shop manual. There are a few sources for shop manuals for the early RX-7s, but in my opinion, only Mazda's own manual is worth spending any money on. The aftermarket offerings from companies like Haynes and Chiltons are often vague or even completely ignorant about the differences from one model year to the next. (It's even worse if you have a GSL-SE.) Popular Mechanics / Alldata also has service information available, either on-line or on a CD-ROM. I have a subscription to their "online manual" for my Volvo, and it seems to be excellent. Most of the diagrams appear to be exact duplicates of the Volvo shop manuals. But I have never seen any of their offerings for the early RX-7s. I do recall reading one comment from an RX-7 owner who was less than enthusiastic about the Alldata offering for his car. He likened it's functionality to that of a vacuum cleaner. In other words, "it sucks."
But the Mazda produced shop manuals are extremely detailed and accurate. Diagrams and photographs are plentiful, and you can expect that any factory options or configurations will be given the attention they deserve. Surprisingly, the manuals are even well written and very readable, given their probable foreign language origins.
You can purchase factory authorized, professionally bound reprints from your local Mazda dealer, MazdaTrix, and Mazda's Competition Parts department. Prices are typically in the $85 to $90 range, plus shipping if you choose one of the mail order vendors. Unfortunately, the quality of pictures in the reprinted manuals is very poor, with a photocopier look to them. Diagrams and charts are reproduced acceptably, but all photos look like black, unintelligible blobs of ink.
A better alternative would be to locate a used copy from the original printing run. The cover and pages may have a few more greasy fingerprints on them, but the photographs will be usable. Used originals range in price from $20 to $100. The average seems to be around $50 or $60. If you can find one for less, consider it a good deal. If you must pay more, well... it'll pay for itself in very little time, so didn't fret about it too much. (Not having the manual will lkely cost you much more than spending too much on it in the first place.) Good sources for used manuals include E-bay, Books4Cars, Autolit and The Rx-7 Parts Trader. Regardless of the cost, there is no better source of information about your RX-7.
One more issue that you should be aware of with the Mazda shop manuals: the wiring diagrams are usually not included in the one volume, depending on which year's manual you're looking for. If you need a manual for model years 1979 through 1982, or for 1984, you'll need to purchase a separate wiring diagram book as well. Both the 1983 and 1985 shop manuals had the wiring diagrams integrated into the single volume. Expect to pay anywhere between $15 and $50 for a used wiring diagram, or $35 to $80 for a new one.