I know of no websites with deep results of US Olympic trials. There's a book which gives complete results of all Olympic trials meets through '92 or '96 by Richard Hymans, published through USATF. I'm pretty sure it's out of print so buying a copy may be impossible, but I've been able to get it through interlibrary loan in the past.
The book in question is "US Olympic Trials Track & Field 1908-1992" by Richard Hymans, published by TAC in 1996. Unfortunately it is out of print and notoriously difficult to find on the second-hand market.