318 question ?

[leroymoparrr]

I just have a crazy question. 318 4bbl HD.What does the HD stand for.??

 

[grumpuscreature]

Heavy Duty, intended for cop cars and taxis.

 

[leroymoparrr]

Heavy Duty, intended for cop cars and taxis.

Thank you.I,m getting to know more on the 81 police interceptor.