RE:Just got my first V8 out of a SC400 and it didn't come with a power steering pump,
If you found a pump, is it possible to do a side by side comparison, or... is it possible for you to find out the dimensions of said PS pump(including any hoses and related hardware, bolts,clamps etc....) and see if they match?
Also, it might help to call your local Lexus dealer, and find out if the part/stock numbers for those pumps match.
Hope I helped!