I agree with Jim, try and get to Dan and Kathy's flat track museum in Fresno Ca. It's only small when compared to big mega millionaire set ups like the Barber museum but it's got a lot of tasty flat trackers and well worth the trip out to Fresno. Dan's wheelchair bound and lately in poor health but is a great bloke and Kathy or one of the volunteers may give you a guided tour.
http://www.vft.org/rouit.html . Tom White's motocross and flat track museum is worth a visit as well, it's in Villa Park in Orange Co, Ca. It's not open to the public except for special days or events but it's worth a call.
http://www.earlyyearsofmx.com/There are usually a lot of Aussies and Kiwis racing at Bonneville, especially in the bike classes. Let's hope it's not rained or washed out. I was hoping to get to Bonneville this year myself but "stuff" has now put my trip back to later in the year.