I know the answer is probably here in the thousands of pages but

Front disc conversion or rear also conversion? I went with Explorer 8.8 with rear disc. Remember that you must change driveshaft also and if going to rear disc about parking brake. Cost for me was about 1800 including cores, aluminum driveshaft, u-joints and spring plates. Also narrowed housing to use same axles, left and right. If staying with 8.25 or 8.75 you must get correct u-bolts and driveshaft to match.
I did end up with 3.27 gears with new Ford motorsports Limited slip and rear discs