What police car? Mine came out of an F Body and I just moved the perches. Got some wheels with 5 inches of back spacing and it works just fine. If you don't feel like going into the guts that may be the way to go.
I am waiting to hear back from the guy on what it came out of.
I am having trouble finding axle width dims online for F/M/J bodies. One site said they are all the same width - do you know if this is true, and if so what the width is? I have seen both 54.34 and 53.34 for flange to flange listed on the internet for the 8.25 F body.