In the past I've used the plain steel radiator mounting kit from Bob Drake, seems to work well. Never had a judge at a show measure the radiator mounting bolt to see if it was correct?
The original dimensions were: 3/8-24 x 2" for the hex bolt with cotter pin hole, 23/32" x 1 1/16" with five coils for the spring, and 3/8-24 (13/32" x 9/16") for the castle nut. The finish on all three was S-2 (black oxide).
