It WILL be an 8-3/4. You can use the entire rear end, including the brakes, if you get it narrowed. If it's got front disc pull those off as C-body discs are hard to find. They are also hard to sell, but somebody will happy you saved them.
If the dash dimmer and headlight are in good shape they will bring as much as $100 (same as 68-70 B-body rallye dash and possibly the standard dash, too).
The 69 Ignition switch is RARE and worth as much as $75 with keys (make a matched set with the door cylinders as these fit every 69 Mopar passenger car).