It sounds like most of the 250R is there, except the engine. Condition is a question though. If there's a lot of rot in the frame, it may all be fair...
Foolishly not looking over the whole trike when I bought it ~10 years ago, I more recently discovered that a previous owner had stripped out the rear...
Partzilla lists the size of the 2-piece wheel O-rings as 176x4.2 (mm)
I took one of my wheel halves to a nearby business with "Rubber and Gasket" in...