I was fortunate to visit it once, in September of 1972, while on my way from the Bay Area back to upstate New York where I worked. The collection was housed in the city of Sparks, Nevada which is just east of Reno. If I remember correctly, it was in a warehouse or industrial district and occupied three or four one-story warehouse-type buildings.
One building was devoted to cars deemed deserving of better display. The others simply had cars jammed together. Some of the collection was systematic. For example, there was at least one Packard from each of the years Packards were built. And I thing the same was largely true for Fords up through 1949 or thereabouts.
Not long ago I scanned many of the 35 mm slides I took with my Nikon F cameras. The Harrah collection photos were taken under poor conditions for the film I was using. The cars were mostly indoors under fluorescent lighting, so the colors I was getting tended into the blue range. Worse, most images were blurred either slightly or strongly. I used my iMac's image software to partly clean up the photos presented below, but the quality is still pretty bad.
Nevertheless, give them a look to get a slight sense of what Harrah had gathered at a point six years before he died.