Police Interceptor Heads?

No such thing as "Police Intercepter heads." Al heads are the same reguardless of application save the 340 T/A or 6 pak heads with the offset intake rocker arm.

The 340 was given a 2.02 intake valve until '73 where it was reduced to a 1.88. All 360 heads have a 1.88 valve.
273 - 318 heads have smaller valves.

Get the casting numbers off the head and or the letter cast into them next to the spark plug holes. Not all heads have a letter.
Casting numbers are located under the head where the 2 intake runners meet.

Stock rebuilt heads are capable of 400 hp, but the manor in which you make 400 hp with stock heads may not be to your likeing. Stock ports and a sizeable street cam can make 360 hp without a problem. Another 40 hp should require a bit more cam.

I take this from example of the old MoPar crate engines. The "Comando" 360 engines came in 2 flavors, 300 and 360 HP. The 360 HP engine was a rebuilt bottom end @ (IIRC) 10-1 ratio, a M1 single plane intake, a Purple 284/.484 cam with stock heads w/2.02 intake valves.

MoPar suggested the rest of this engine parts as followed;

Holley 750
Large tube heads

The heads you mention, for $400 sounds like an OK deal, but, would need porting to achieve your goal. A bowl porting with a performance valve job & back cutting of the valves would be the perscription I'd order up.

Still a reasonable amount of money spent.