Rear diff question

HI It sounds like you have a very mild motor , by the time you cut your housing if you can do that and buy shorter axles or have your axle shorten for a ford 9'' good strong rear if your building a full track car. You can buy a 8 1/4 posi rear that will be good for 375 hp cheep . have picked them up for $350 there a a lot of these around or 8 3/4 rear there are some guys out there that don't want your arm and leg four them but they are at swap meets most of the time , this rear will be good for at least 800hp and more . I have picked up a body housings for as little as $150.00 and 849 posi housing for $ for $175 to $350 yes would put a bearing kit in them , And a body axles for$ 50 a pair to $ 100.00 . but this takes some looking around . Hope this is of some help to you