I'm sure he used the 250 radiators. The lower frame cradle on a 250r Is tapered from the front to the cross over tube that has one foot peg bolt Into It. The 500 engine Is lower In the front compaired to the 250. When the frame tubes were put back In they were made to clear the 500 engine. He lost a little of the taper In the front of the lower cradle, but no total ground clearance. The replacement tubes were welded Into the cross tube In the same place as the origionals.