Continuing on, Don Strack's web site has the following listings for the power cars:

[utahrails.net]

Scroll down the page to "UPP 207 through 209" and notice how he describes their HEP application.

For those not familiar with Mr. Strack's work, he's a former UP Mechanical Department employee who now, amoung other things, maintains the Utahrails web site. I consider him to be to UP diesel locomtive history what Joe Strapac is to SP diesel locomotive history.