I think it would make a decent road car. Crown Vics are supposed to be reliable and since they made a load of them, parts are pretty much everywhere. Gas mileage might be a bit low and it is rwd so if it snows a lot then there might me trouble, also its kind of heavy and slow.
If you buy an actual Crown Vic police interceptor(CVPI) then you should consider one important factor
Police tend to leave there cars on the whole time, this leads to things like a worn out camshaft.
If you get a civilian model than you can upgrade it with parts from a CVPI.
CVPI have upgraded trans and oil cooler, heavy duty suspension, chassy stuffing, and more powerful alternators, not to mention you can buy a bad *** push bar lol