[3macs1]

I have parted a few 68 police cars over the years and remember quite a few in our home town where they had 6 alone in the 68 body style.
I remember nothing special about the 427 385 hp engines other than they had a special oil filter adapter to use the old cannister vs the spin on. None were two doors and none were red.Not saying they could not be. In fact I have never seen a true police package in red.Fire Dept vehicles yes.
90% had the power disc brakes with rally wheels and just the police caps, special ball joints, special seats, wiring etc. But nothing was consistent. Some had F41 and posi and some didnot some had 140 speedo and others didnot, some had rear window winders others the windows were fixed.
Did I ever see a 427 425 hp factory in a police car.Yes twice and both were original. Both were 4 door black interceptors, bench seat 4 spds, with standard brakes and steering, smog, open element air cleaner, chrome covers and a 68 buick steering wheel. Both had tach and guages, 140 speedo and no radio.Also memeo or copo was on the cowl tag.
I would do some more digging with people that may remember your dad's car to try to determine if it was a true police package.Cloning a police package correctly would not be easy pending how detailed you would like to go.
To answer your question yes a 425 HP 427 was a option in a 68 cop car.