I am not sure of the difference between Avgas and Racing Fuel, but I think you are on the right track. I have religiously used racing fuel (110 octane) since the early 90's and have never had a problem with the tank, fuel line or carb.
For the 315R, the part numbers for the two caliper brakes bolts are: 96300-08032-00 Bolt, Flange, 8-32 and 96300-08055-00 Bolt, Flange, 8-55.
For the 4RT, the part numbers are: 90113-NN4-000 Bolt, Socket 8X33 and 90114-NN4-000 Bolt, Socket 8X55