I use the downloadable FAA registration database. Most builders tend to use some sort of variation in the "common" name for the aircraft, and I search on that. For instance, I search for "RV-8" , "RV8", "RV 8", etc.
There are outlyers, of course. When developing my filters, I make them pretty general and narrow them down as needed to exclude other types.
Favorite case was a "BEDE-Four".....
Ron Wanttaja