Alaska RailRoad GP40-2s with HEP

Have the Alaska RailRoad GP40-2s had HEP ever since they were delivered, or has it been retrofitted in recent years?

Some of these units may have been retrofitted when they were delivered to the Alaska Railroad when they came from Conrail in the 80's.

the ARR GP40's with HEP are all original ARR units. they were retrofitted in the early 90's. I don't know where the work was done. The have modified long hoods with 4 fans instead of 3 and the rear end is flat as apposed to the normal more pointed end of regular GP40's.

So what did the ARR use for their passenger trains before this? Did they keep the FP7s that long, or was something else used in between (AFAIK HEP was introduced with the ex-UP passenger cars in the early 80s)?

A few GP40's came from Conrail in the 70's or 80's?? and more than likley a few of them may have been retrofitted once they arrived on ARR rails??

They had an E9B for a while that supplied either HEP or steam, can't remember which. Do the SD70's have HEP? I seem to recall some of them being so-equipped, but I see lots of pics of the SD70's pulling passenger trains with power cars.