What about the reinforced frame for example?
I see a lot of references out there to "extra welds" and a "reinforced frame" but do we have any proof that anything was actually different? My guess would be more welds or gussets on the K-member and shock/spring mounts. Maybe something similar to the torque boxes on hemi cars. The cast K-frame biscuits didn't even come out until the 80s.
You'll see references to the "special handling" tags that usually came on patrol cars, and in many cases that's all it means - special attention to assembly. The police steering boxes were double checked for tolerances and hand selected but they were just regular production boxes.
Chrysler was willing to bend over backwards for large departments with huge fleet orders like CHP who held their feet to the fire for custom packages. I believe there were also patrol and pursuit packages. In other words, a police car is not necessarily an A38 car, and all A38 cars are not equal to one another.
These were all stout cars in their most basic form and unless you are going to push one into fleet service I wouldn't be too worried about one holding together. Larger cooling systems and things like that were off the shelf items necessary for a car that potentially needed to run 24/7 and go from idling for an hour to a quick 70 mph response across town and back to idling for a hour and stop-go-stop-go patrol duty. Chrysler had better motors, transmissions, brakes, suspensions and rears right out of the gate.
Like I said some of the A38 package included things like wiring upgrades - these cars usually had a higher output alternator and battery for things like lights and sirens, and they would bypass the firewall bulkhead on some models. Nice to have but not necessary to have for even a daily driver.
If you are serious about buying one of these cars, and it doesn't
have to be an A38 package car, look for the cleanest one you can find with the motor size you want and AC (bigger rad standard). I had a no-frills 78 Monaco with a 318 and highway gears and while it wasn't too strong down low, it would break 100 mph with ease on the highway. The ride was phenomenal but not sporty - would love to drive one some day with HD torsion bars!