8 3/4 rear end help

i was looking for an 8 3/4 rear end and found one that came out of a drag car dart body style. my question is this rear end is about 4 ft wide...much smaller than the typical rear end but it has extended axles and he has the rims to go with them and they are about 10 in across .....does this sound right at all and will this fit under my 72 demon