The HD version of the 360 also has an air pump, IIRC.

 

I missed that part.

 

ok, so now we are talking about 4th gens? The 4th gens have LD and HD?

I know, for a fact, that there were packages like this:

My 2001 has the option "Heavy duty cooling package" under OPTIONS for the sticker.

It was known that the HD was the diesel from people you talk to. They usually ask "Is it a HD?" Meaning gas or diesel.

 

Not to dig up an old post or anything (its not THAT old) but I believe the HD is High Durability. I have been trying to find an exact difference myself. At least that is the description from ATK Engines for the HD12 (SD is the DD72). I have seen the option for HD 360 parts in parts stores as well.

Taken from their catalog:
DD72: FI, GAS, OHV, FOR MAN TRANSMISSIONS CUSTOMERS MUST PURCHACE CHRYSLER
PART # 53009180 PILOT SLEEVE BEARING, PEDESTAL MOUNTED ROCKER ARMS,
ROLLER CAM

HD12: FI, GAS, OHV, FOR MAN TRANSMISSIONS CUSTOMERS MUST PURCHACE CHRYSLER
PART # 53009180 PILOT SLEEVE BEARING, PEDESTAL MOUNTED ROCKER ARMS,
ROLLER CAM, HIGH DURABILITY ENGINE

Both are listed for 93-01 5.9L 8 cyl 360ci motors, with Z in the VIN, although I have heard that it it ends in a 5 for it to be the HD version.(source

If you look at parts from most part stores (thinking NAPA and Advanced off the top of my head) they offer Heavy Duty gaskets and some other 'HD' parts for the gasser 5.9. The head gaskets are a little bit thicker (edit: they were different brands so it could just be the material+design the brand uses), but I don't know if there is any other difference. For the 1500 it does not list the HD engine. They are probably the designation for the gas 5.9's that came in the 2500. and/or maybe 3500? I've also heard the 2500HD's had an EGR when the SD/LD's did not. I'm sure dodge or an engine re-manufacturer could answer. The HD crate motor also costs about $500 more, so what makes it cost $500 more?

 

Double post. no option to delete.

 

I believe my 97 service manual indicated that the hd had dual exhaust along with dual cats. I have a 97 2500 8800gvw and it has the 2 into one exhaust spec'd with the ld. I was under the impression that chassis cabs might have been built with this engine.